18815521957 has 4 divisors (see below), whose sum is σ = 18815798016. Its totient is φ = 18815245900.

The previous prime is 18815521927. The next prime is 18815521961. The reversal of 18815521957 is 75912551881.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18815521957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18815521927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45948 + ... + 199354.

It is an arithmetic number, because the mean of its divisors is an integer number (4703949504).

Almost surely, 2^18815521957 is an apocalyptic number.

It is an amenable number.

18815521957 is a deficient number, since it is larger than the sum of its proper divisors (276059).

18815521957 is a wasteful number, since it uses less digits than its factorization.

18815521957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 276058.

The product of its digits is 1008000, while the sum is 52.

The spelling of 18815521957 in words is "eighteen billion, eight hundred fifteen million, five hundred twenty-one thousand, nine hundred fifty-seven".