21550931 has 6 divisors (see below), whose sum is σ = 22529220. Its totient is φ = 20613428.

The previous prime is 21550901. The next prime is 21550937. The reversal of 21550931 is 13905512.

It is not a de Polignac number, because 21550931 - 2¹⁴ = 21534547 is a prime.

It is a super-2 number, since 2×21550931² = 928885253933522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21550931.

It is not an unprimeable number, because it can be changed into a prime (21550937) 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 5 ways as a sum of consecutive naturals, for example, 19841 + ... + 20898.

It is an arithmetic number, because the mean of its divisors is an integer number (3754870).

Almost surely, 2^21550931 is an apocalyptic number.

21550931 is a deficient number, since it is larger than the sum of its proper divisors (978289).

21550931 is an equidigital number, since it uses as much as digits as its factorization.

21550931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40785 (or 40762 counting only the distinct ones).

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 21550931 is about 4642.2980300709. The cubic root of 21550931 is about 278.2842829728.

The spelling of 21550931 in words is "twenty-one million, five hundred fifty thousand, nine hundred thirty-one".