81515233 has 2 divisors, whose sum is σ = 81515234. Its totient is φ = 81515232.

The previous prime is 81515209. The next prime is 81515261. The reversal of 81515233 is 33251518.

It is an a-pointer prime, because the next prime (81515261) can be obtained adding 81515233 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72795024 + 8720209 = 8532^2 + 2953^2 .

It is a cyclic number.

It is not a de Polignac number, because 81515233 - 2¹⁷ = 81384161 is a prime.

It is a super-2 number, since 2×81515233² = 13289466422088578, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81515293) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40757616 + 40757617.

It is an arithmetic number, because the mean of its divisors is an integer number (40757617).

Almost surely, 2^81515233 is an apocalyptic number.

It is an amenable number.

81515233 is a deficient number, since it is larger than the sum of its proper divisors (1).

81515233 is an equidigital number, since it uses as much as digits as its factorization.

81515233 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3600, while the sum is 28.

The square root of 81515233 is about 9028.5786810550. The cubic root of 81515233 is about 433.5903334792.

The spelling of 81515233 in words is "eighty-one million, five hundred fifteen thousand, two hundred thirty-three".