81019657 has 2 divisors, whose sum is σ = 81019658. Its totient is φ = 81019656.

The previous prime is 81019643. The next prime is 81019661. The reversal of 81019657 is 75691018.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66243321 + 14776336 = 8139^2 + 3844^2 .

It is a cyclic number.

It is not a de Polignac number, because 81019657 - 2¹¹ = 81017609 is a prime.

It is not a weakly prime, because it can be changed into another prime (81011657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40509828 + 40509829.

It is an arithmetic number, because the mean of its divisors is an integer number (40509829).

Almost surely, 2^81019657 is an apocalyptic number.

It is an amenable number.

81019657 is a deficient number, since it is larger than the sum of its proper divisors (1).

81019657 is an equidigital number, since it uses as much as digits as its factorization.

81019657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 37.

The square root of 81019657 is about 9001.0919893089. The cubic root of 81019657 is about 432.7098686314.

The spelling of 81019657 in words is "eighty-one million, nineteen thousand, six hundred fifty-seven".