21656604071 has 4 divisors (see below), whose sum is σ = 21724921752. Its totient is φ = 21588286392.

The previous prime is 21656604029. The next prime is 21656604089. The reversal of 21656604071 is 17040665612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21656604071 - 2³⁰ = 20582862247 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 (21656604001) 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, 34158365 + ... + 34158998.

It is an arithmetic number, because the mean of its divisors is an integer number (5431230438).

Almost surely, 2^21656604071 is an apocalyptic number.

21656604071 is a deficient number, since it is larger than the sum of its proper divisors (68317681).

21656604071 is an equidigital number, since it uses as much as digits as its factorization.

21656604071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68317680.

The product of its (nonzero) digits is 60480, while the sum is 38.

The spelling of 21656604071 in words is "twenty-one billion, six hundred fifty-six million, six hundred four thousand, seventy-one".