21667956 has 12 divisors (see below), whose sum is σ = 50558592. Its totient is φ = 7222648.

The previous prime is 21667951. The next prime is 21667969. The reversal of 21667956 is 65976612.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21667951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 902820 + ... + 902843.

It is an arithmetic number, because the mean of its divisors is an integer number (4213216).

Almost surely, 2^21667956 is an apocalyptic number.

It is an amenable number.

21667956 is an abundant number, since it is smaller than the sum of its proper divisors (28890636).

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

21667956 is a wasteful number, since it uses less digits than its factorization.

21667956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1805670 (or 1805668 counting only the distinct ones).

The product of its digits is 136080, while the sum is 42.

The square root of 21667956 is about 4654.8851758126. The cubic root of 21667956 is about 278.7870833516.

The spelling of 21667956 in words is "twenty-one million, six hundred sixty-seven thousand, nine hundred fifty-six".