21158087 has 4 divisors (see below), whose sum is σ = 21238800. Its totient is φ = 21077376.

The previous prime is 21158063. The next prime is 21158119. The reversal of 21158087 is 78085112.

It is a happy number.

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 21158087 - 2⁸ = 21157831 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 (21158057) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39962 + ... + 40487.

It is an arithmetic number, because the mean of its divisors is an integer number (5309700).

Almost surely, 2^21158087 is an apocalyptic number.

21158087 is a deficient number, since it is larger than the sum of its proper divisors (80713).

21158087 is an equidigital number, since it uses as much as digits as its factorization.

21158087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80712.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21158087 is about 4599.7920605175. The cubic root of 21158087 is about 276.5829893233.

Subtracting 21158087 from its reverse (78085112), we obtain a square (56927025 = 7545²).

The spelling of 21158087 in words is "twenty-one million, one hundred fifty-eight thousand, eighty-seven".