The properties of a Higgs boson candidate are measured in the H→ZZ→4ℓ decay channel, with ℓ=e, μ, using data from pp collisions corresponding to an integrated luminosity of 5.1  fb−1 at the center-of-mass energy of s=7  TeV and 19.7  fb-1 at s=8  TeV, recorded with the CMS detector at the LHC. The new boson is observed as a narrow resonance with a local significance of 6.8 standard deviations, a measured mass of 125.6±0.4(stat)±0.2(syst)  GeV, and a total width ≤3.4  GeV at the 95% confidence level. The production cross section of the new boson times its branching fraction to four leptons is measured to be 0.93-0.23+0.26(stat)-0.09+0.13(syst) times that predicted by the standard model. Its spin-parity properties are found to be consistent with the expectations for the standard-model Higgs boson. The hypotheses of a pseudoscalar and all tested spin-1 boson hypotheses are excluded at the 99% confidence level or higher. All tested spin-2 boson hypotheses are excluded at the 95% confidence level or higher.