64397981 has 2 divisors, whose sum is σ = 64397982. Its totient is φ = 64397980.

The previous prime is 64397959. The next prime is 64397987. The reversal of 64397981 is 18979346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45778756 + 18619225 = 6766^2 + 4315^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64397981 is a prime.

It is a super-2 number, since 2×64397981² = 8294199913752722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64397987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32198990 + 32198991.

It is an arithmetic number, because the mean of its divisors is an integer number (32198991).

Almost surely, 2^64397981 is an apocalyptic number.

It is an amenable number.

64397981 is a deficient number, since it is larger than the sum of its proper divisors (1).

64397981 is an equidigital number, since it uses as much as digits as its factorization.

64397981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 47.

The square root of 64397981 is about 8024.8352631067. The cubic root of 64397981 is about 400.8274143669.

The spelling of 64397981 in words is "sixty-four million, three hundred ninety-seven thousand, nine hundred eighty-one".