21251955 has 16 divisors (see below), whose sum is σ = 36003744. Its totient is φ = 10667520.

The previous prime is 21251941. The next prime is 21251987. The reversal of 21251955 is 55915212.

It is not a de Polignac number, because 21251955 - 2¹⁶ = 21186419 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41416 + ... + 41925.

It is an arithmetic number, because the mean of its divisors is an integer number (2250234).

Almost surely, 2^21251955 is an apocalyptic number.

21251955 is a deficient number, since it is larger than the sum of its proper divisors (14751789).

21251955 is a wasteful number, since it uses less digits than its factorization.

21251955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83366.

The product of its digits is 4500, while the sum is 30.

The square root of 21251955 is about 4609.9842732920. The cubic root of 21251955 is about 276.9914067199.

The spelling of 21251955 in words is "twenty-one million, two hundred fifty-one thousand, nine hundred fifty-five".