64999991 has 16 divisors (see below), whose sum is σ = 77663040. Its totient is φ = 53222400.

The previous prime is 64999981. The next prime is 65000011. The reversal of 64999991 is 19999946.

It is not a de Polignac number, because 64999991 - 2⁶ = 64999927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64999981) 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, 18041 + ... + 21341.

It is an arithmetic number, because the mean of its divisors is an integer number (4853940).

Almost surely, 2^64999991 is an apocalyptic number.

64999991 is a deficient number, since it is larger than the sum of its proper divisors (12663049).

64999991 is a wasteful number, since it uses less digits than its factorization.

64999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3434.

The product of its digits is 1417176, while the sum is 56.

The square root of 64999991 is about 8062.2571901422. The cubic root of 64999991 is about 402.0725573017.

The spelling of 64999991 in words is "sixty-four million, nine hundred ninety-nine thousand, nine hundred ninety-one".