666990720 has 512 divisors, whose sum is σ = 2687904000. Its totient is φ = 156119040.

The previous prime is 666990719. The next prime is 666990757. The reversal of 666990720 is 27099666.

It is a super-2 number, since 2×666990720² = 889753241132236800, 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 Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 22999666 + ... + 22999694.

Almost surely, 2^666990720 is an apocalyptic number.

666990720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666990720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1343952000).

666990720 is an abundant number, since it is smaller than the sum of its proper divisors (2020913280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666990720 is a wasteful number, since it uses less digits than its factorization.

666990720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90 (or 50 counting only the distinct ones).

The product of its (nonzero) digits is 244944, while the sum is 45.

The square root of 666990720 is about 25826.1634781475. The cubic root of 666990720 is about 873.7219851395.

The spelling of 666990720 in words is "six hundred sixty-six million, nine hundred ninety thousand, seven hundred twenty".