21277881 has 12 divisors (see below), whose sum is σ = 30960852. Its totient is φ = 14080896.

The previous prime is 21277871. The next prime is 21277901. The reversal of 21277881 is 18877212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5405625 + 15872256 = 2325^2 + 3984^2 .

It is not a de Polignac number, because 21277881 - 2¹¹ = 21275833 is a prime.

It is a super-2 number, since 2×21277881² = 905496439700322, which contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21277831) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7396 + ... + 9861.

It is an arithmetic number, because the mean of its divisors is an integer number (2580071).

Almost surely, 2^21277881 is an apocalyptic number.

21277881 is the 2466-th nonagonal number.

It is an amenable number.

21277881 is a deficient number, since it is larger than the sum of its proper divisors (9682971).

21277881 is a wasteful number, since it uses less digits than its factorization.

21277881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17400 (or 17397 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21277881 is about 4612.7953563972. The cubic root of 21277881 is about 277.1039981020.

The spelling of 21277881 in words is "twenty-one million, two hundred seventy-seven thousand, eight hundred eighty-one".