37991813 has 2 divisors, whose sum is σ = 37991814. Its totient is φ = 37991812.

The previous prime is 37991801. The next prime is 37991861. The reversal of 37991813 is 31819973.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 35438209 + 2553604 = 5953^2 + 1598^2 .

It is an emirp because it is prime and its reverse (31819973) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 37991813 - 2⁶ = 37991749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (37991873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 18995906 + 18995907.

It is an arithmetic number, because the mean of its divisors is an integer number (18995907).

Almost surely, 2^37991813 is an apocalyptic number.

It is an amenable number.

37991813 is a deficient number, since it is larger than the sum of its proper divisors (1).

37991813 is an equidigital number, since it uses as much as digits as its factorization.

37991813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40824, while the sum is 41.

The square root of 37991813 is about 6163.7499138106. The cubic root of 37991813 is about 336.1733946539.

The spelling of 37991813 in words is "thirty-seven million, nine hundred ninety-one thousand, eight hundred thirteen".