81617491 has 2 divisors, whose sum is σ = 81617492. Its totient is φ = 81617490.

The previous prime is 81617479. The next prime is 81617519. The reversal of 81617491 is 19471618.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81617491 is a prime.

It is a super-2 number, since 2×81617491² = 13322829674270162, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81617491.

It is not a weakly prime, because it can be changed into another prime (81617441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40808745 + 40808746.

It is an arithmetic number, because the mean of its divisors is an integer number (40808746).

Almost surely, 2^81617491 is an apocalyptic number.

81617491 is a deficient number, since it is larger than the sum of its proper divisors (1).

81617491 is an equidigital number, since it uses as much as digits as its factorization.

81617491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 37.

The square root of 81617491 is about 9034.2399237567. The cubic root of 81617491 is about 433.7715656711.

The spelling of 81617491 in words is "eighty-one million, six hundred seventeen thousand, four hundred ninety-one".