21159556 has 24 divisors (see below), whose sum is σ = 40543776. Its totient is φ = 9582720.

The previous prime is 21159539. The next prime is 21159587. The reversal of 21159556 is 65595112.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14115 + ... + 15541.

It is an arithmetic number, because the mean of its divisors is an integer number (1689324).

Almost surely, 2^21159556 is an apocalyptic number.

It is an amenable number.

21159556 is a deficient number, since it is larger than the sum of its proper divisors (19384220).

21159556 is a wasteful number, since it uses less digits than its factorization.

21159556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1779 (or 1777 counting only the distinct ones).

The product of its digits is 13500, while the sum is 34.

The square root of 21159556 is about 4599.9517388773. The cubic root of 21159556 is about 276.5893902014.

Subtracting 21159556 from its reverse (65595112), we obtain a square (44435556 = 6666²).

The spelling of 21159556 in words is "twenty-one million, one hundred fifty-nine thousand, five hundred fifty-six".