81397777 has 2 divisors, whose sum is σ = 81397778. Its totient is φ = 81397776.

The previous prime is 81397769. The next prime is 81397781. The reversal of 81397777 is 77779318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 46457856 + 34939921 = 6816^2 + 5911^2 .

It is a cyclic number.

It is not a de Polignac number, because 81397777 - 2³ = 81397769 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81397777.

It is a weakly prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40698888 + 40698889.

It is an arithmetic number, because the mean of its divisors is an integer number (40698889).

Almost surely, 2^81397777 is an apocalyptic number.

It is an amenable number.

81397777 is a deficient number, since it is larger than the sum of its proper divisors (1).

81397777 is an equidigital number, since it uses as much as digits as its factorization.

81397777 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 518616, while the sum is 49.

The square root of 81397777 is about 9022.0716578843. The cubic root of 81397777 is about 433.3819786941.

The spelling of 81397777 in words is "eighty-one million, three hundred ninety-seven thousand, seven hundred seventy-seven".