81616651 has 2 divisors, whose sum is σ = 81616652. Its totient is φ = 81616650.

The previous prime is 81616637. The next prime is 81616657. The reversal of 81616651 is 15661618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81616651 - 2¹³ = 81608459 is a prime.

It is a super-2 number, since 2×81616651² = 13322555440911602, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81616657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40808325 + 40808326.

It is an arithmetic number, because the mean of its divisors is an integer number (40808326).

Almost surely, 2^81616651 is an apocalyptic number.

81616651 is a deficient number, since it is larger than the sum of its proper divisors (1).

81616651 is an equidigital number, since it uses as much as digits as its factorization.

81616651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 34.

The square root of 81616651 is about 9034.1934338379. The cubic root of 81616651 is about 433.7700775531.

The spelling of 81616651 in words is "eighty-one million, six hundred sixteen thousand, six hundred fifty-one".