665622981 has 32 divisors (see below), whose sum is σ = 1046908800. Its totient is φ = 416528640.

The previous prime is 665622959. The next prime is 665623001. The reversal of 665622981 is 189226566.

665622981 is a `hidden beast` number, since 6 + 6 + 562 + 2 + 9 + 81 = 666.

It is not a de Polignac number, because 665622981 - 2¹⁴ = 665606597 is a prime.

It is a super-2 number, since 2×665622981² = 886107905670652722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665622281) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 190591 + ... + 194051.

It is an arithmetic number, because the mean of its divisors is an integer number (32715900).

Almost surely, 2^665622981 is an apocalyptic number.

It is an amenable number.

665622981 is a deficient number, since it is larger than the sum of its proper divisors (381285819).

665622981 is a wasteful number, since it uses less digits than its factorization.

665622981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3906 (or 3900 counting only the distinct ones).

The product of its digits is 311040, while the sum is 45.

The square root of 665622981 is about 25799.6701723103. The cubic root of 665622981 is about 873.1243549309.

The spelling of 665622981 in words is "six hundred sixty-five million, six hundred twenty-two thousand, nine hundred eighty-one".