81894557 has 2 divisors, whose sum is σ = 81894558. Its totient is φ = 81894556.

The previous prime is 81894551. The next prime is 81894581. The reversal of 81894557 is 75549818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70375321 + 11519236 = 8389^2 + 3394^2 .

It is a cyclic number.

It is not a de Polignac number, because 81894557 - 2⁶ = 81894493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81894551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40947278 + 40947279.

It is an arithmetic number, because the mean of its divisors is an integer number (40947279).

Almost surely, 2^81894557 is an apocalyptic number.

It is an amenable number.

81894557 is a deficient number, since it is larger than the sum of its proper divisors (1).

81894557 is an equidigital number, since it uses as much as digits as its factorization.

81894557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 403200, while the sum is 47.

The square root of 81894557 is about 9049.5611495807. The cubic root of 81894557 is about 434.2618511561.

The spelling of 81894557 in words is "eighty-one million, eight hundred ninety-four thousand, five hundred fifty-seven".