664737981 has 8 divisors (see below), whose sum is σ = 894161280. Its totient is φ = 439236672.

The previous prime is 664737977. The next prime is 664738003. The reversal of 664737981 is 189737466.

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

It is not a de Polignac number, because 664737981 - 2² = 664737977 is a prime.

It is a super-2 number, since 2×664737981² = 883753166767912722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664737911) 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, 980101 + ... + 980778.

It is an arithmetic number, because the mean of its divisors is an integer number (111770160).

Almost surely, 2^664737981 is an apocalyptic number.

It is an amenable number.

664737981 is a deficient number, since it is larger than the sum of its proper divisors (229423299).

664737981 is a wasteful number, since it uses less digits than its factorization.

664737981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1960995.

The product of its digits is 1524096, while the sum is 51.

The square root of 664737981 is about 25782.5130854228. The cubic root of 664737981 is about 872.7372199752.

The spelling of 664737981 in words is "six hundred sixty-four million, seven hundred thirty-seven thousand, nine hundred eighty-one".