21506777544640 has 56 divisors (see below), whose sum is σ = 51254685440640. Its totient is φ = 8595711095808.

The previous prime is 21506777544613. The next prime is 21506777544727. The reversal of 21506777544640 is 4644577760512.

It is a super-3 number, since 3×21506777544640³ (a number of 41 digits) contains 333 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, 26949552 + ... + 27736111.

Almost surely, 2^{21506777544640} is an apocalyptic number.

21506777544640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21506777544640 is an abundant number, since it is smaller than the sum of its proper divisors (29747907896000).

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

21506777544640 is a wasteful number, since it uses less digits than its factorization.

21506777544640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54686909 (or 54686899 counting only the distinct ones).

The product of its (nonzero) digits is 39513600, while the sum is 58.

The spelling of 21506777544640 in words is "twenty-one trillion, five hundred six billion, seven hundred seventy-seven million, five hundred forty-four thousand, six hundred forty".