81660407 has 2 divisors, whose sum is σ = 81660408. Its totient is φ = 81660406.

The previous prime is 81660391. The next prime is 81660409. The reversal of 81660407 is 70406618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81660407 - 2⁴ = 81660391 is a prime.

Together with 81660409, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81660409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40830203 + 40830204.

It is an arithmetic number, because the mean of its divisors is an integer number (40830204).

Almost surely, 2^81660407 is an apocalyptic number.

81660407 is a deficient number, since it is larger than the sum of its proper divisors (1).

81660407 is an equidigital number, since it uses as much as digits as its factorization.

81660407 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 81660407 is about 9036.6147975888. The cubic root of 81660407 is about 433.8475807442.

The spelling of 81660407 in words is "eighty-one million, six hundred sixty thousand, four hundred seven".