81688091 has 2 divisors, whose sum is σ = 81688092. Its totient is φ = 81688090.

The previous prime is 81688081. The next prime is 81688097. The reversal of 81688091 is 19088618.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81688091 is a prime.

It is a super-2 number, since 2×81688091² = 13345888422448562, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81688097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40844045 + 40844046.

It is an arithmetic number, because the mean of its divisors is an integer number (40844046).

Almost surely, 2^81688091 is an apocalyptic number.

81688091 is a deficient number, since it is larger than the sum of its proper divisors (1).

81688091 is an equidigital number, since it uses as much as digits as its factorization.

81688091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27648, while the sum is 41.

The square root of 81688091 is about 9038.1464360786. The cubic root of 81688091 is about 433.8966019687.

The spelling of 81688091 in words is "eighty-one million, six hundred eighty-eight thousand, ninety-one".