81686651 has 2 divisors, whose sum is σ = 81686652. Its totient is φ = 81686650.

The previous prime is 81686617. The next prime is 81686653. The reversal of 81686651 is 15668618.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81686651 - 2⁶ = 81686587 is a prime.

Together with 81686653, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81686599 and 81686608.

It is not a weakly prime, because it can be changed into another prime (81686653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40843325 + 40843326.

It is an arithmetic number, because the mean of its divisors is an integer number (40843326).

Almost surely, 2^81686651 is an apocalyptic number.

81686651 is a deficient number, since it is larger than the sum of its proper divisors (1).

81686651 is an equidigital number, since it uses as much as digits as its factorization.

81686651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69120, while the sum is 41.

The square root of 81686651 is about 9038.0667733758. The cubic root of 81686651 is about 433.8940523731.

The spelling of 81686651 in words is "eighty-one million, six hundred eighty-six thousand, six hundred fifty-one".