21187056 has 40 divisors (see below), whose sum is σ = 59710464. Its totient is φ = 6420160.

The previous prime is 21187027. The next prime is 21187063. The reversal of 21187056 is 65078112.

It is a congruent number.

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, 19536 + ... + 20591.

Almost surely, 2^21187056 is an apocalyptic number.

It is an amenable number.

21187056 is an abundant number, since it is smaller than the sum of its proper divisors (38523408).

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

21187056 is a wasteful number, since it uses less digits than its factorization.

21187056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40149 (or 40143 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21187056 is about 4602.9399300882. The cubic root of 21187056 is about 276.7091613893.

It can be divided in two parts, 2118705 and 6, that added together give a triangular number (2118711 = T₂₀₅₈).

The spelling of 21187056 in words is "twenty-one million, one hundred eighty-seven thousand, fifty-six".