81379631 has 2 divisors, whose sum is σ = 81379632. Its totient is φ = 81379630.

The previous prime is 81379609. The next prime is 81379633. The reversal of 81379631 is 13697318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81379631 - 2¹⁰ = 81378607 is a prime.

It is a super-2 number, since 2×81379631² = 13245288683392322, which contains 22 as substring.

Together with 81379633, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81379633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40689815 + 40689816.

It is an arithmetic number, because the mean of its divisors is an integer number (40689816).

Almost surely, 2^81379631 is an apocalyptic number.

81379631 is a deficient number, since it is larger than the sum of its proper divisors (1).

81379631 is an equidigital number, since it uses as much as digits as its factorization.

81379631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 38.

The square root of 81379631 is about 9021.0659569698. The cubic root of 81379631 is about 433.3497716972.

The spelling of 81379631 in words is "eighty-one million, three hundred seventy-nine thousand, six hundred thirty-one".