21521031717 has 8 divisors (see below), whose sum is σ = 29057933440. Its totient is φ = 14165742240.

The previous prime is 21521031709. The next prime is 21521031757. The reversal of 21521031717 is 71713012512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21521031717 - 2³ = 21521031709 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 (21521031757) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45402784 + ... + 45403257.

It is an arithmetic number, because the mean of its divisors is an integer number (3632241680).

Almost surely, 2^21521031717 is an apocalyptic number.

It is an amenable number.

21521031717 is a deficient number, since it is larger than the sum of its proper divisors (7536901723).

21521031717 is an equidigital number, since it uses as much as digits as its factorization.

21521031717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90806123.

The product of its (nonzero) digits is 2940, while the sum is 30.

The spelling of 21521031717 in words is "twenty-one billion, five hundred twenty-one million, thirty-one thousand, seven hundred seventeen".