21901956 has 12 divisors (see below), whose sum is σ = 51104592. Its totient is φ = 7300648.

The previous prime is 21901909. The next prime is 21901969. The reversal of 21901956 is 65910912.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 912570 + ... + 912593.

It is an arithmetic number, because the mean of its divisors is an integer number (4258716).

Almost surely, 2^21901956 is an apocalyptic number.

It is an amenable number.

21901956 is an abundant number, since it is smaller than the sum of its proper divisors (29202636).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21901956 is a wasteful number, since it uses less digits than its factorization.

21901956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1825170 (or 1825168 counting only the distinct ones).

The product of its (nonzero) digits is 4860, while the sum is 33.

The square root of 21901956 is about 4679.9525638622. The cubic root of 21901956 is about 279.7870660005.

The spelling of 21901956 in words is "twenty-one million, nine hundred one thousand, nine hundred fifty-six".