21851956 has 24 divisors (see below), whose sum is σ = 44142336. Its totient is φ = 9271200.

The previous prime is 21851927. The next prime is 21851959. The reversal of 21851956 is 65915812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21851959) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1036 + ... + 6691.

It is an arithmetic number, because the mean of its divisors is an integer number (1839264).

Almost surely, 2^21851956 is an apocalyptic number.

It is an amenable number.

21851956 is an abundant number, since it is smaller than the sum of its proper divisors (22290380).

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

21851956 is a wasteful number, since it uses less digits than its factorization.

21851956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7839 (or 7837 counting only the distinct ones).

The product of its digits is 21600, while the sum is 37.

The square root of 21851956 is about 4674.6075771128. The cubic root of 21851956 is about 279.5739950422.

The spelling of 21851956 in words is "twenty-one million, eight hundred fifty-one thousand, nine hundred fifty-six".