21056087 has 4 divisors (see below), whose sum is σ = 22675800. Its totient is φ = 19436376.

The previous prime is 21056069. The next prime is 21056089. The reversal of 21056087 is 78065012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21056087 - 2¹⁰ = 21055063 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056089) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 809837 + ... + 809862.

It is an arithmetic number, because the mean of its divisors is an integer number (5668950).

Almost surely, 2^21056087 is an apocalyptic number.

21056087 is a deficient number, since it is larger than the sum of its proper divisors (1619713).

21056087 is a wasteful number, since it uses less digits than its factorization.

21056087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1619712.

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 21056087 is about 4588.6912077410. The cubic root of 21056087 is about 276.1378179939.

It can be divided in two parts, 2105 and 6087, that added together give a 13-th power (8192 = 2¹³).

The spelling of 21056087 in words is "twenty-one million, fifty-six thousand, eighty-seven".