81361997 has 2 divisors, whose sum is σ = 81361998. Its totient is φ = 81361996.

The previous prime is 81361991. The next prime is 81362027. The reversal of 81361997 is 79916318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77774761 + 3587236 = 8819^2 + 1894^2 .

It is a cyclic number.

It is not a de Polignac number, because 81361997 - 2⁴ = 81361981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81361991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40680998 + 40680999.

It is an arithmetic number, because the mean of its divisors is an integer number (40680999).

Almost surely, 2^81361997 is an apocalyptic number.

It is an amenable number.

81361997 is a deficient number, since it is larger than the sum of its proper divisors (1).

81361997 is an equidigital number, since it uses as much as digits as its factorization.

81361997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 81648, while the sum is 44.

The square root of 81361997 is about 9020.0885250645. The cubic root of 81361997 is about 433.3184688524.

The spelling of 81361997 in words is "eighty-one million, three hundred sixty-one thousand, nine hundred ninety-seven".