20505115557 has 12 divisors (see below), whose sum is σ = 29768850540. Its totient is φ = 13600684608.

The previous prime is 20505115459. The next prime is 20505115559. The reversal of 20505115557 is 75551150502.

20505115557 is a `hidden beast` number, since 2 + 0 + 50 + 51 + 1 + 5 + 557 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 20219133636 + 285981921 = 142194^2 + 16911^2 .

It is not a de Polignac number, because 20505115557 - 2¹⁵ = 20505082789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20505115559) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5780832 + ... + 5784377.

It is an arithmetic number, because the mean of its divisors is an integer number (2480737545).

Almost surely, 2^20505115557 is an apocalyptic number.

It is an amenable number.

20505115557 is a deficient number, since it is larger than the sum of its proper divisors (9263734983).

20505115557 is a wasteful number, since it uses less digits than its factorization.

20505115557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11565412 (or 11565409 counting only the distinct ones).

The product of its (nonzero) digits is 43750, while the sum is 36.

The spelling of 20505115557 in words is "twenty billion, five hundred five million, one hundred fifteen thousand, five hundred fifty-seven".