21877281 has 24 divisors (see below), whose sum is σ = 33033000. Its totient is φ = 13934592.

The previous prime is 21877279. The next prime is 21877291. The reversal of 21877281 is 18277812.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4161600 + 17715681 = 2040^2 + 4209^2 .

It is not a de Polignac number, because 21877281 - 2¹ = 21877279 is a prime.

It is a super-2 number, since 2×21877281² = 957230847905922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21877241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 28065 + ... + 28833.

It is an arithmetic number, because the mean of its divisors is an integer number (1376375).

Almost surely, 2^21877281 is an apocalyptic number.

It is an amenable number.

21877281 is a deficient number, since it is larger than the sum of its proper divisors (11155719).

21877281 is a wasteful number, since it uses less digits than its factorization.

21877281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913 (or 910 counting only the distinct ones).

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

The square root of 21877281 is about 4677.3155762681. The cubic root of 21877281 is about 279.6819560567.

The spelling of 21877281 in words is "twenty-one million, eight hundred seventy-seven thousand, two hundred eighty-one".