668699640 has 192 divisors, whose sum is σ = 2493504000. Its totient is φ = 152246016.

The previous prime is 668699621. The next prime is 668699663. The reversal of 668699640 is 46996866.

It is a happy number.

It is a super-2 number, since 2×668699640² = 894318417072259200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1116061 + ... + 1116659.

It is an arithmetic number, because the mean of its divisors is an integer number (12987000).

Almost surely, 2^668699640 is an apocalyptic number.

668699640 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 668699640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1246752000).

668699640 is an abundant number, since it is smaller than the sum of its proper divisors (1824804360).

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

668699640 is a wasteful number, since it uses less digits than its factorization.

668699640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1066 (or 1059 counting only the distinct ones).

The product of its (nonzero) digits is 3359232, while the sum is 54.

The square root of 668699640 is about 25859.2273666481. The cubic root of 668699640 is about 874.4675465343.

The spelling of 668699640 in words is "six hundred sixty-eight million, six hundred ninety-nine thousand, six hundred forty".