21170520661 has 8 divisors (see below), whose sum is σ = 21218939840. Its totient is φ = 21122132832.

The previous prime is 21170520653. The next prime is 21170520671. The reversal of 21170520661 is 16602507112.

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 21170520661 - 2³ = 21170520653 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 (21170520671) 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, 1805305 + ... + 1816993.

It is an arithmetic number, because the mean of its divisors is an integer number (2652367480).

Almost surely, 2^21170520661 is an apocalyptic number.

It is an amenable number.

21170520661 is a deficient number, since it is larger than the sum of its proper divisors (48419179).

21170520661 is a wasteful number, since it uses less digits than its factorization.

21170520661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15675.

The product of its (nonzero) digits is 5040, while the sum is 31.

The spelling of 21170520661 in words is "twenty-one billion, one hundred seventy million, five hundred twenty thousand, six hundred sixty-one".