21135956 has 6 divisors (see below), whose sum is σ = 36987930. Its totient is φ = 10567976.

The previous prime is 21135911. The next prime is 21135971. The reversal of 21135956 is 65953112.

It can be written as a sum of positive squares in only one way, i.e., 13104400 + 8031556 = 3620^2 + 2834^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2641991 + ... + 2641998.

It is an arithmetic number, because the mean of its divisors is an integer number (6164655).

Almost surely, 2^21135956 is an apocalyptic number.

It is an amenable number.

21135956 is a deficient number, since it is larger than the sum of its proper divisors (15851974).

21135956 is a wasteful number, since it uses less digits than its factorization.

21135956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5283993 (or 5283991 counting only the distinct ones).

The product of its digits is 8100, while the sum is 32.

The square root of 21135956 is about 4597.3857788965. The cubic root of 21135956 is about 276.4865219764.

The spelling of 21135956 in words is "twenty-one million, one hundred thirty-five thousand, nine hundred fifty-six".