21706700657 has 4 divisors (see below), whose sum is σ = 21950596260. Its totient is φ = 21462805056.

The previous prime is 21706700633. The next prime is 21706700671. The reversal of 21706700657 is 75600760712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 9101923216 + 12604777441 = 95404^2 + 112271^2 .

It is a cyclic number.

It is not a de Polignac number, because 21706700657 - 2¹⁶ = 21706635121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21706702657) 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, 121947668 + ... + 121947845.

It is an arithmetic number, because the mean of its divisors is an integer number (5487649065).

Almost surely, 2^21706700657 is an apocalyptic number.

It is an amenable number.

21706700657 is a deficient number, since it is larger than the sum of its proper divisors (243895603).

21706700657 is an equidigital number, since it uses as much as digits as its factorization.

21706700657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243895602.

The product of its (nonzero) digits is 123480, while the sum is 41.

The spelling of 21706700657 in words is "twenty-one billion, seven hundred six million, seven hundred thousand, six hundred fifty-seven".