81399377 has 2 divisors, whose sum is σ = 81399378. Its totient is φ = 81399376.

The previous prime is 81399313. The next prime is 81399379. The reversal of 81399377 is 77399318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 59459521 + 21939856 = 7711^2 + 4684^2 .

It is a cyclic number.

It is not a de Polignac number, because 81399377 - 2⁶ = 81399313 is a prime.

Together with 81399379, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81399379) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40699688 + 40699689.

It is an arithmetic number, because the mean of its divisors is an integer number (40699689).

Almost surely, 2^81399377 is an apocalyptic number.

It is an amenable number.

81399377 is a deficient number, since it is larger than the sum of its proper divisors (1).

81399377 is an equidigital number, since it uses as much as digits as its factorization.

81399377 is an evil number, because the sum of its binary digits is even.

The product of its digits is 285768, while the sum is 47.

The square root of 81399377 is about 9022.1603288791. The cubic root of 81399377 is about 433.3848182746.

The spelling of 81399377 in words is "eighty-one million, three hundred ninety-nine thousand, three hundred seventy-seven".