37891981 has 2 divisors, whose sum is σ = 37891982. Its totient is φ = 37891980.

The previous prime is 37891969. The next prime is 37891993. The reversal of 37891981 is 18919873.

It is a balanced prime because it is at equal distance from previous prime (37891969) and next prime (37891993).

It can be written as a sum of positive squares in only one way, i.e., 25704900 + 12187081 = 5070^2 + 3491^2 .

It is a cyclic number.

It is not a de Polignac number, because 37891981 - 2¹³ = 37883789 is a prime.

It is a super-2 number, since 2×37891981² = 2871604448208722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (37891921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 18945990 + 18945991.

It is an arithmetic number, because the mean of its divisors is an integer number (18945991).

Almost surely, 2^37891981 is an apocalyptic number.

It is an amenable number.

37891981 is a deficient number, since it is larger than the sum of its proper divisors (1).

37891981 is an equidigital number, since it uses as much as digits as its factorization.

37891981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108864, while the sum is 46.

The square root of 37891981 is about 6155.6462698891. The cubic root of 37891981 is about 335.8786793903.

The spelling of 37891981 in words is "thirty-seven million, eight hundred ninety-one thousand, nine hundred eighty-one".