81302581 has 2 divisors, whose sum is σ = 81302582. Its totient is φ = 81302580.

The previous prime is 81302521. The next prime is 81302593. The reversal of 81302581 is 18520318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 41486481 + 39816100 = 6441^2 + 6310^2 .

It is a cyclic number.

It is not a de Polignac number, because 81302581 - 2⁷ = 81302453 is a prime.

It is a super-2 number, since 2×81302581² = 13220219354523122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81302521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40651290 + 40651291.

It is an arithmetic number, because the mean of its divisors is an integer number (40651291).

Almost surely, 2^81302581 is an apocalyptic number.

It is an amenable number.

81302581 is a deficient number, since it is larger than the sum of its proper divisors (1).

81302581 is an equidigital number, since it uses as much as digits as its factorization.

81302581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 81302581 is about 9016.7943860332. The cubic root of 81302581 is about 433.2129637402.

Adding to 81302581 its reverse (18520318), we get a palindrome (99822899).

The spelling of 81302581 in words is "eighty-one million, three hundred two thousand, five hundred eighty-one".