20713521 has 4 divisors (see below), whose sum is σ = 27618032. Its totient is φ = 13809012.

The previous prime is 20713489. The next prime is 20713529. The reversal of 20713521 is 12531702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20713521 - 2⁵ = 20713489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20713529) 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, 3452251 + ... + 3452256.

It is an arithmetic number, because the mean of its divisors is an integer number (6904508).

Almost surely, 2^20713521 is an apocalyptic number.

It is an amenable number.

20713521 is a deficient number, since it is larger than the sum of its proper divisors (6904511).

20713521 is an equidigital number, since it uses as much as digits as its factorization.

20713521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6904510.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 20713521 is about 4551.2109377615. The cubic root of 20713521 is about 274.6321075053.

The spelling of 20713521 in words is "twenty million, seven hundred thirteen thousand, five hundred twenty-one".