21557011561 has 8 divisors (see below), whose sum is σ = 21589129760. Its totient is φ = 21524916672.

The previous prime is 21557011559. The next prime is 21557011631. The reversal of 21557011561 is 16511075512.

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 21557011561 - 2¹ = 21557011559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21557015561) 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, 2703166 + ... + 2711128.

It is an arithmetic number, because the mean of its divisors is an integer number (2698641220).

Almost surely, 2^21557011561 is an apocalyptic number.

It is an amenable number.

21557011561 is a deficient number, since it is larger than the sum of its proper divisors (32118199).

21557011561 is a wasteful number, since it uses less digits than its factorization.

21557011561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11655.

The product of its (nonzero) digits is 10500, while the sum is 34.

The spelling of 21557011561 in words is "twenty-one billion, five hundred fifty-seven million, eleven thousand, five hundred sixty-one".