81581233 has 2 divisors, whose sum is σ = 81581234. Its totient is φ = 81581232.

The previous prime is 81581197. The next prime is 81581261. The reversal of 81581233 is 33218518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 51022449 + 30558784 = 7143^2 + 5528^2 .

It is a cyclic number.

It is not a de Polignac number, because 81581233 - 2²⁵ = 48026801 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81581195 and 81581204.

It is not a weakly prime, because it can be changed into another prime (81581273) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40790616 + 40790617.

It is an arithmetic number, because the mean of its divisors is an integer number (40790617).

Almost surely, 2^81581233 is an apocalyptic number.

It is an amenable number.

81581233 is a deficient number, since it is larger than the sum of its proper divisors (1).

81581233 is an equidigital number, since it uses as much as digits as its factorization.

81581233 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5760, while the sum is 31.

The square root of 81581233 is about 9032.2330018661. The cubic root of 81581233 is about 433.7073228281.

The spelling of 81581233 in words is "eighty-one million, five hundred eighty-one thousand, two hundred thirty-three".