668960640 has 128 divisors (see below), whose sum is σ = 2369296800. Its totient is φ = 178384896.

The previous prime is 668960623. The next prime is 668960657. The reversal of 668960640 is 46069866.

It is an interprime number because it is at equal distance from previous prime (668960623) and next prime (668960657).

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2077 + ... + 36636.

Almost surely, 2^668960640 is an apocalyptic number.

668960640 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 668960640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1184648400).

668960640 is an abundant number, since it is smaller than the sum of its proper divisors (1700336160).

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

668960640 is a wasteful number, since it uses less digits than its factorization.

668960640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38741 (or 38723 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 668960640 is about 25864.2734288052. The cubic root of 668960640 is about 874.5813028100.

The spelling of 668960640 in words is "six hundred sixty-eight million, nine hundred sixty thousand, six hundred forty".