21713539 has 4 divisors (see below), whose sum is σ = 22990824. Its totient is φ = 20436256.

The previous prime is 21713521. The next prime is 21713567. The reversal of 21713539 is 93531712.

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 21713539 - 2²³ = 13324931 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21713539.

It is not an unprimeable number, because it can be changed into a prime (21713509) 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, 638617 + ... + 638650.

It is an arithmetic number, because the mean of its divisors is an integer number (5747706).

Almost surely, 2^21713539 is an apocalyptic number.

21713539 is a deficient number, since it is larger than the sum of its proper divisors (1277285).

21713539 is a wasteful number, since it uses less digits than its factorization.

21713539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1277284.

The product of its digits is 5670, while the sum is 31.

The square root of 21713539 is about 4659.7788574137. The cubic root of 21713539 is about 278.9824417379.

The spelling of 21713539 in words is "twenty-one million, seven hundred thirteen thousand, five hundred thirty-nine".