81617551 has 2 divisors, whose sum is σ = 81617552. Its totient is φ = 81617550.

The previous prime is 81617531. The next prime is 81617609. The reversal of 81617551 is 15571618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81617551 - 2⁵ = 81617519 is a prime.

It is a super-2 number, since 2×81617551² = 13322849262475202, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81617531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40808775 + 40808776.

It is an arithmetic number, because the mean of its divisors is an integer number (40808776).

Almost surely, 2^81617551 is an apocalyptic number.

81617551 is a deficient number, since it is larger than the sum of its proper divisors (1).

81617551 is an equidigital number, since it uses as much as digits as its factorization.

81617551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8400, while the sum is 34.

The square root of 81617551 is about 9034.2432444561. The cubic root of 81617551 is about 433.7716719649.

The spelling of 81617551 in words is "eighty-one million, six hundred seventeen thousand, five hundred fifty-one".