81557243 has 2 divisors, whose sum is σ = 81557244. Its totient is φ = 81557242.

The previous prime is 81557239. The next prime is 81557257. The reversal of 81557243 is 34275518.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81557243 - 2² = 81557239 is a prime.

It is a super-2 number, since 2×81557243² = 13303167771522098, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81557843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40778621 + 40778622.

It is an arithmetic number, because the mean of its divisors is an integer number (40778622).

Almost surely, 2^81557243 is an apocalyptic number.

81557243 is a deficient number, since it is larger than the sum of its proper divisors (1).

81557243 is an equidigital number, since it uses as much as digits as its factorization.

81557243 is an evil number, because the sum of its binary digits is even.

The product of its digits is 33600, while the sum is 35.

The square root of 81557243 is about 9030.9048826793. The cubic root of 81557243 is about 433.6648062741.

The spelling of 81557243 in words is "eighty-one million, five hundred fifty-seven thousand, two hundred forty-three".