64661891 has 8 divisors (see below), whose sum is σ = 75111264. Its totient is φ = 54515520.

The previous prime is 64661881. The next prime is 64661893. The reversal of 64661891 is 19816646.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64661891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (64661893) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75290 + ... + 76143.

It is an arithmetic number, because the mean of its divisors is an integer number (9388908).

Almost surely, 2^64661891 is an apocalyptic number.

64661891 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

64661891 is a deficient number, since it is larger than the sum of its proper divisors (10449373).

64661891 is a wasteful number, since it uses less digits than its factorization.

64661891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151501.

The product of its digits is 62208, while the sum is 41.

The square root of 64661891 is about 8041.2617790991. The cubic root of 64661891 is about 401.3742130232.

The spelling of 64661891 in words is "sixty-four million, six hundred sixty-one thousand, eight hundred ninety-one".