21052139 has 4 divisors (see below), whose sum is σ = 21348720. Its totient is φ = 20755560.

The previous prime is 21052127. The next prime is 21052159. The reversal of 21052139 is 93125012.

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 21052139 - 2²⁰ = 20003563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21052159) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 148184 + ... + 148325.

It is an arithmetic number, because the mean of its divisors is an integer number (5337180).

Almost surely, 2^21052139 is an apocalyptic number.

21052139 is a deficient number, since it is larger than the sum of its proper divisors (296581).

21052139 is an equidigital number, since it uses as much as digits as its factorization.

21052139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296580.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21052139 is about 4588.2609995509. The cubic root of 21052139 is about 276.1205583728.

The spelling of 21052139 in words is "twenty-one million, fifty-two thousand, one hundred thirty-nine".