18971660021 has 8 divisors (see below), whose sum is σ = 19083999000. Its totient is φ = 18859599360.

The previous prime is 18971659951. The next prime is 18971660039. The reversal of 18971660021 is 12006617981.

It can be written as a sum of positive squares in 4 ways, for example, as 338044996 + 18633615025 = 18386^2 + 136505^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18971660021 - 2²² = 18967465717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18971660041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 67955 + ... + 206303.

It is an arithmetic number, because the mean of its divisors is an integer number (2385499875).

Almost surely, 2^18971660021 is an apocalyptic number.

It is an amenable number.

18971660021 is a deficient number, since it is larger than the sum of its proper divisors (112338979).

18971660021 is a wasteful number, since it uses less digits than its factorization.

18971660021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139159.

The product of its (nonzero) digits is 36288, while the sum is 41.

The spelling of 18971660021 in words is "eighteen billion, nine hundred seventy-one million, six hundred sixty thousand, twenty-one".