21200618978640 has 160 divisors (see below), whose sum is σ = 73031279448960. Its totient is φ = 5652962251776.

The previous prime is 21200618978597. The next prime is 21200618978647. The reversal of 21200618978640 is 4687981600212.

It is a happy number.

21200618978640 is a `hidden beast` number, since 2 + 12 + 0 + 0 + 618 + 9 + 7 + 8 + 6 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21200618978647) 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, 22580652 + ... + 23500788.

It is an arithmetic number, because the mean of its divisors is an integer number (456445496556).

Almost surely, 2^{21200618978640} is an apocalyptic number.

21200618978640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21200618978640 is an abundant number, since it is smaller than the sum of its proper divisors (51830660470320).

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

21200618978640 is a wasteful number, since it uses less digits than its factorization.

21200618978640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 930826 (or 930814 counting only the distinct ones).

The product of its (nonzero) digits is 2322432, while the sum is 54.

The spelling of 21200618978640 in words is "twenty-one trillion, two hundred billion, six hundred eighteen million, nine hundred seventy-eight thousand, six hundred forty".