166404391 has 2 divisors, whose sum is σ = 166404392. Its totient is φ = 166404390.

The previous prime is 166404383. The next prime is 166404409. The reversal of 166404391 is 193404661.

166404391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 166404391 - 2³ = 166404383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166404331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83202195 + 83202196.

It is an arithmetic number, because the mean of its divisors is an integer number (83202196).

Almost surely, 2^166404391 is an apocalyptic number.

166404391 is a deficient number, since it is larger than the sum of its proper divisors (1).

166404391 is an equidigital number, since it uses as much as digits as its factorization.

166404391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15552, while the sum is 34.

The square root of 166404391 is about 12899.7825950673. The cubic root of 166404391 is about 550.0323848699.

The spelling of 166404391 in words is "one hundred sixty-six million, four hundred four thousand, three hundred ninety-one".