18777961721537 has 2 divisors, whose sum is σ = 18777961721538. Its totient is φ = 18777961721536.

The previous prime is 18777961721501. The next prime is 18777961721543. The reversal of 18777961721537 is 73512716977781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13549989222961 + 5227972498576 = 3681031^2 + 2286476^2 .

It is an emirp because it is prime and its reverse (73512716977781) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18777961721537 - 2²² = 18777957527233 is a prime.

It is a super-2 number, since 2×18777961721537² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18777961721587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9388980860768 + 9388980860769.

It is an arithmetic number, because the mean of its divisors is an integer number (9388980860769).

Almost surely, 2^{18777961721537} is an apocalyptic number.

It is an amenable number.

18777961721537 is a deficient number, since it is larger than the sum of its proper divisors (1).

18777961721537 is an equidigital number, since it uses as much as digits as its factorization.

18777961721537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 217818720, while the sum is 71.

The spelling of 18777961721537 in words is "eighteen trillion, seven hundred seventy-seven billion, nine hundred sixty-one million, seven hundred twenty-one thousand, five hundred thirty-seven".