21357616660 has 24 divisors (see below), whose sum is σ = 46397582280. Its totient is φ = 8248458624.

The previous prime is 21357616601. The next prime is 21357616673. The reversal of 21357616660 is 6661675312.

It can be written as a sum of positive squares in 4 ways, for example, as 7637711236 + 13719905424 = 87394^2 + 117132^2 .

It is a super-2 number, since 2×21357616660² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18411159 + ... + 18412318.

It is an arithmetic number, because the mean of its divisors is an integer number (1933232595).

Almost surely, 2^21357616660 is an apocalyptic number.

21357616660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21357616660 is an abundant number, since it is smaller than the sum of its proper divisors (25039965620).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21357616660 is a wasteful number, since it uses less digits than its factorization.

21357616660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36823515 (or 36823513 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 43.

The spelling of 21357616660 in words is "twenty-one billion, three hundred fifty-seven million, six hundred sixteen thousand, six hundred sixty".