21159956 has 18 divisors (see below), whose sum is σ = 37924362. Its totient is φ = 10330320.

The previous prime is 21159953. The next prime is 21159973. The reversal of 21159956 is 65995112.

It can be written as a sum of positive squares in only one way, i.e., 18490000 + 2669956 = 4300^2 + 1634^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21159953) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5966 + ... + 8826.

It is an arithmetic number, because the mean of its divisors is an integer number (2106909).

Almost surely, 2^21159956 is an apocalyptic number.

It is an amenable number.

21159956 is a deficient number, since it is larger than the sum of its proper divisors (16764406).

21159956 is a wasteful number, since it uses less digits than its factorization.

21159956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2951 (or 2906 counting only the distinct ones).

The product of its digits is 24300, while the sum is 38.

The square root of 21159956 is about 4599.9952173888. The cubic root of 21159956 is about 276.5911330713.

The spelling of 21159956 in words is "twenty-one million, one hundred fifty-nine thousand, nine hundred fifty-six".