21660271557 has 32 divisors (see below), whose sum is σ = 31363096320. Its totient is φ = 13245772800.

The previous prime is 21660271543. The next prime is 21660271583. The reversal of 21660271557 is 75517206612.

It is a happy number.

It is not a de Polignac number, because 21660271557 - 2¹⁴ = 21660255173 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21660271517) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 381619 + ... + 434687.

It is an arithmetic number, because the mean of its divisors is an integer number (980096760).

Almost surely, 2^21660271557 is an apocalyptic number.

It is an amenable number.

21660271557 is a deficient number, since it is larger than the sum of its proper divisors (9702824763).

21660271557 is a wasteful number, since it uses less digits than its factorization.

21660271557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53293.

The product of its (nonzero) digits is 176400, while the sum is 42.

The spelling of 21660271557 in words is "twenty-one billion, six hundred sixty million, two hundred seventy-one thousand, five hundred fifty-seven".