21704731621 has 8 divisors (see below), whose sum is σ = 21965567040. Its totient is φ = 21444273312.

The previous prime is 21704731571. The next prime is 21704731627. The reversal of 21704731621 is 12613740712.

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

It is a cyclic number.

It is not a de Polignac number, because 21704731621 - 2⁹ = 21704731109 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 (21704731627) 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, 22386 + ... + 209548.

It is an arithmetic number, because the mean of its divisors is an integer number (2745695880).

Almost surely, 2^21704731621 is an apocalyptic number.

It is an amenable number.

21704731621 is a deficient number, since it is larger than the sum of its proper divisors (260835419).

21704731621 is a wasteful number, since it uses less digits than its factorization.

21704731621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188555.

The product of its (nonzero) digits is 14112, while the sum is 34.

Subtracting from 21704731621 its reverse (12613740712), we obtain a palindrome (9090990909).

The spelling of 21704731621 in words is "twenty-one billion, seven hundred four million, seven hundred thirty-one thousand, six hundred twenty-one".