664343981 has 16 divisors (see below), whose sum is σ = 784739328. Its totient is φ = 550368000.

The previous prime is 664343921. The next prime is 664343989. The reversal of 664343981 is 189343466.

It is a de Polignac number, because none of the positive numbers 2^k-664343981 is a prime.

It is a super-2 number, since 2×664343981² = 882705850181856722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664343989) 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, 235781 + ... + 238581.

It is an arithmetic number, because the mean of its divisors is an integer number (49046208).

Almost surely, 2^664343981 is an apocalyptic number.

It is an amenable number.

664343981 is a deficient number, since it is larger than the sum of its proper divisors (120395347).

664343981 is a wasteful number, since it uses less digits than its factorization.

664343981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3932.

The product of its digits is 373248, while the sum is 44.

The square root of 664343981 is about 25774.8711150997. The cubic root of 664343981 is about 872.5647578254.

The spelling of 664343981 in words is "six hundred sixty-four million, three hundred forty-three thousand, nine hundred eighty-one".