18557377891921 has 4 divisors (see below), whose sum is σ = 20244412245744. Its totient is φ = 16870343538100.

The previous prime is 18557377891799. The next prime is 18557377891931. The reversal of 18557377891921 is 12919877375581.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18557377891921 is a prime.

It is a super-3 number, since 3×18557377891921³ (a number of 41 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18557377891931) 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, 843517176895 + ... + 843517176916.

It is an arithmetic number, because the mean of its divisors is an integer number (5061103061436).

Almost surely, 2^{18557377891921} is an apocalyptic number.

18557377891921 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18557377891921 is a deficient number, since it is larger than the sum of its proper divisors (1687034353823).

18557377891921 is a wasteful number, since it uses less digits than its factorization.

18557377891921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1687034353822.

The product of its digits is 266716800, while the sum is 73.

The spelling of 18557377891921 in words is "eighteen trillion, five hundred fifty-seven billion, three hundred seventy-seven million, eight hundred ninety-one thousand, nine hundred twenty-one".