64138981 has 4 divisors (see below), whose sum is σ = 66350700. Its totient is φ = 61927264.

The previous prime is 64138961. The next prime is 64138993. The reversal of 64138981 is 18983146.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 45346756 + 18792225 = 6734^2 + 4335^2 .

It is a cyclic number.

It is not a de Polignac number, because 64138981 - 2⁷ = 64138853 is a prime.

It is a super-2 number, since 2×64138981² = 8227617767436722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64138951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1105816 + ... + 1105873.

It is an arithmetic number, because the mean of its divisors is an integer number (16587675).

Almost surely, 2^64138981 is an apocalyptic number.

It is an amenable number.

64138981 is a deficient number, since it is larger than the sum of its proper divisors (2211719).

64138981 is a wasteful number, since it uses less digits than its factorization.

64138981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2211718.

The product of its digits is 41472, while the sum is 40.

The square root of 64138981 is about 8008.6816018618. The cubic root of 64138981 is about 400.2893344135.

The spelling of 64138981 in words is "sixty-four million, one hundred thirty-eight thousand, nine hundred eighty-one".