66905391 has 16 divisors (see below), whose sum is σ = 102187008. Its totient is φ = 38143200.

The previous prime is 66905381. The next prime is 66905429. The reversal of 66905391 is 19350966.

It is not a de Polignac number, because 66905391 - 2¹⁷ = 66774319 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66905341) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6226 + ... + 13136.

It is an arithmetic number, because the mean of its divisors is an integer number (6386688).

Almost surely, 2^66905391 is an apocalyptic number.

66905391 is a deficient number, since it is larger than the sum of its proper divisors (35281617).

66905391 is a wasteful number, since it uses less digits than its factorization.

66905391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7382.

The product of its (nonzero) digits is 43740, while the sum is 39.

The square root of 66905391 is about 8179.5715657973. The cubic root of 66905391 is about 405.9635463562.

The spelling of 66905391 in words is "sixty-six million, nine hundred five thousand, three hundred ninety-one".