21627981 has 24 divisors (see below), whose sum is σ = 32849856. Its totient is φ = 13685760.

The previous prime is 21627967. The next prime is 21628001. The reversal of 21627981 is 18972612.

21627981 is a `hidden beast` number, since 21 + 627 + 9 + 8 + 1 = 666.

It is not a de Polignac number, because 21627981 - 2¹³ = 21619789 is a prime.

It is a super-2 number, since 2×21627981² = 935539124272722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21627901) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33421 + ... + 34061.

It is an arithmetic number, because the mean of its divisors is an integer number (1368744).

Almost surely, 2^21627981 is an apocalyptic number.

It is an amenable number.

21627981 is a deficient number, since it is larger than the sum of its proper divisors (11221875).

21627981 is a wasteful number, since it uses less digits than its factorization.

21627981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833 (or 830 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21627981 is about 4650.5893174951. The cubic root of 21627981 is about 278.6155339577.

The spelling of 21627981 in words is "twenty-one million, six hundred twenty-seven thousand, nine hundred eighty-one".