21506777471640 has 32 divisors (see below), whose sum is σ = 64520332415280. Its totient is φ = 5735140659072.

The previous prime is 21506777471537. The next prime is 21506777471681. The reversal of 21506777471640 is 4617477760512.

It is a happy number.

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, 89611572679 + ... + 89611572918.

Almost surely, 2^{21506777471640} is an apocalyptic number.

21506777471640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21506777471640 is an abundant number, since it is smaller than the sum of its proper divisors (43013554943640).

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

21506777471640 is a wasteful number, since it uses less digits than its factorization.

21506777471640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179223145611 (or 179223145607 counting only the distinct ones).

The product of its (nonzero) digits is 13829760, while the sum is 57.

The spelling of 21506777471640 in words is "twenty-one trillion, five hundred six billion, seven hundred seventy-seven million, four hundred seventy-one thousand, six hundred forty".