21138956 has 12 divisors (see below), whose sum is σ = 39169368. Its totient is φ = 9947712.

The previous prime is 21138937. The next prime is 21138959. The reversal of 21138956 is 65983112.

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21138959) 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, 155366 + ... + 155501.

It is an arithmetic number, because the mean of its divisors is an integer number (3264114).

Almost surely, 2^21138956 is an apocalyptic number.

It is an amenable number.

21138956 is a deficient number, since it is larger than the sum of its proper divisors (18030412).

21138956 is a wasteful number, since it uses less digits than its factorization.

21138956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310888 (or 310886 counting only the distinct ones).

The product of its digits is 12960, while the sum is 35.

The square root of 21138956 is about 4597.7120396997. The cubic root of 21138956 is about 276.4996026926.

The spelling of 21138956 in words is "twenty-one million, one hundred thirty-eight thousand, nine hundred fifty-six".