38991991 has 2 divisors, whose sum is σ = 38991992. Its totient is φ = 38991990.

The previous prime is 38991973. The next prime is 38992003. The reversal of 38991991 is 19919983.

It is a strong prime.

It is an emirp because it is prime and its reverse (19919983) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 38991991 - 2⁹ = 38991479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (38991961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19495995 + 19495996.

It is an arithmetic number, because the mean of its divisors is an integer number (19495996).

Almost surely, 2^38991991 is an apocalyptic number.

38991991 is a deficient number, since it is larger than the sum of its proper divisors (1).

38991991 is an equidigital number, since it uses as much as digits as its factorization.

38991991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 157464, while the sum is 49.

The square root of 38991991 is about 6244.3567322824. The cubic root of 38991991 is about 339.0979288554.

The spelling of 38991991 in words is "thirty-eight million, nine hundred ninety-one thousand, nine hundred ninety-one".