21680957693 has 4 divisors (see below), whose sum is σ = 21740034240. Its totient is φ = 21621881148.

The previous prime is 21680957663. The next prime is 21680957759. The reversal of 21680957693 is 39675908612.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 21680957693 - 2⁶ = 21680957629 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 (21680957663) 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, 29537723 + ... + 29538456.

It is an arithmetic number, because the mean of its divisors is an integer number (5435008560).

Almost surely, 2^21680957693 is an apocalyptic number.

It is an amenable number.

21680957693 is a deficient number, since it is larger than the sum of its proper divisors (59076547).

21680957693 is an equidigital number, since it uses as much as digits as its factorization.

21680957693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59076546.

The product of its (nonzero) digits is 4898880, while the sum is 56.

The spelling of 21680957693 in words is "twenty-one billion, six hundred eighty million, nine hundred fifty-seven thousand, six hundred ninety-three".