21157308451818 has 192 divisors, whose sum is σ = 61629628354560. Its totient is φ = 5256473888160.

The previous prime is 21157308451777. The next prime is 21157308451891. The reversal of 21157308451818 is 81815480375112.

21157308451818 is a `hidden beast` number, since 2 + 1 + 1 + 5 + 7 + 30 + 84 + 518 + 18 = 666.

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

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 9004030 + ... + 11107977.

It is an arithmetic number, because the mean of its divisors is an integer number (320987647680).

Almost surely, 2^{21157308451818} is an apocalyptic number.

21157308451818 is an abundant number, since it is smaller than the sum of its proper divisors (40472319902742).

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

21157308451818 is a wasteful number, since it uses less digits than its factorization.

21157308451818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20112070 (or 20112053 counting only the distinct ones).

The product of its (nonzero) digits is 2150400, while the sum is 54.

The spelling of 21157308451818 in words is "twenty-one trillion, one hundred fifty-seven billion, three hundred eight million, four hundred fifty-one thousand, eight hundred eighteen".