18991377437 has 2 divisors, whose sum is σ = 18991377438. Its totient is φ = 18991377436.

The previous prime is 18991377389. The next prime is 18991377473. The reversal of 18991377437 is 73477319981.

It is a happy number.

Together with next prime (18991377473) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16100056996 + 2891320441 = 126886^2 + 53771^2 .

It is a cyclic number.

It is not a de Polignac number, because 18991377437 - 2¹⁶ = 18991311901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18991377487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9495688718 + 9495688719.

It is an arithmetic number, because the mean of its divisors is an integer number (9495688719).

Almost surely, 2^18991377437 is an apocalyptic number.

It is an amenable number.

18991377437 is a deficient number, since it is larger than the sum of its proper divisors (1).

18991377437 is an equidigital number, since it uses as much as digits as its factorization.

18991377437 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8001504, while the sum is 59.

The spelling of 18991377437 in words is "eighteen billion, nine hundred ninety-one million, three hundred seventy-seven thousand, four hundred thirty-seven".