20990775618 has 30 divisors (see below), whose sum is σ = 47039018499. Its totient is φ = 6996310524.

The previous prime is 20990775581. The next prime is 20990775623. The reversal of 20990775618 is 81657709902.

20990775618 is a `hidden beast` number, since 2 + 0 + 9 + 9 + 0 + 77 + 561 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 10495387809 + 10495387809 = 102447^2 + 102447^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=102447.

It is a super-2 number, since 2×20990775618² (a number of 21 digits) contains 22 as substring.

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 14 ways as a sum of consecutive naturals, for example, 1838355 + ... + 1849737.

Almost surely, 2^20990775618 is an apocalyptic number.

20990775618 is an abundant number, since it is smaller than the sum of its proper divisors (26048242881).

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

20990775618 is an frugal number, since it uses more digits than its factorization.

20990775618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22780 (or 11388 counting only the distinct ones).

The product of its (nonzero) digits is 1905120, while the sum is 54.

The spelling of 20990775618 in words is "twenty billion, nine hundred ninety million, seven hundred seventy-five thousand, six hundred eighteen".