1277961891 has 16 divisors (see below), whose sum is σ = 1731115776. Its totient is φ = 838493856.

The previous prime is 1277961863. The next prime is 1277961901. The reversal of 1277961891 is 1981697721.

It is a happy number.

It is not a de Polignac number, because 1277961891 - 2⁶ = 1277961827 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1277961851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37681 + ... + 63053.

It is an arithmetic number, because the mean of its divisors is an integer number (108194736).

Almost surely, 2^1277961891 is an apocalyptic number.

1277961891 is a deficient number, since it is larger than the sum of its proper divisors (453153885).

1277961891 is a wasteful number, since it uses less digits than its factorization.

1277961891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25642.

The product of its digits is 381024, while the sum is 51.

The square root of 1277961891 is about 35748.5928534257. The cubic root of 1277961891 is about 1085.1904614428.

The spelling of 1277961891 in words is "one billion, two hundred seventy-seven million, nine hundred sixty-one thousand, eight hundred ninety-one".