21656706697 has 4 divisors (see below), whose sum is σ = 21657002256. Its totient is φ = 21656411140.

The previous prime is 21656706683. The next prime is 21656706703. The reversal of 21656706697 is 79660765612.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21656706697 - 2⁷ = 21656706569 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21656706667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53658 + ... + 214924.

It is an arithmetic number, because the mean of its divisors is an integer number (5414250564).

Almost surely, 2^21656706697 is an apocalyptic number.

It is an amenable number.

21656706697 is a deficient number, since it is larger than the sum of its proper divisors (295559).

21656706697 is a wasteful number, since it uses less digits than its factorization.

21656706697 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 295558.

The product of its (nonzero) digits is 5715360, while the sum is 55.

The spelling of 21656706697 in words is "twenty-one billion, six hundred fifty-six million, seven hundred six thousand, six hundred ninety-seven".