688740661 has 8 divisors (see below), whose sum is σ = 788088320. Its totient is φ = 589632048.

The previous prime is 688740659. The next prime is 688740667. The reversal of 688740661 is 166047886.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 688740661 - 2¹ = 688740659 is a prime.

It is a super-2 number, since 2×688740661² = 948727396229433842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688740667) 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, 53541 + ... + 65146.

It is an arithmetic number, because the mean of its divisors is an integer number (98511040).

Almost surely, 2^688740661 is an apocalyptic number.

It is an amenable number.

688740661 is a deficient number, since it is larger than the sum of its proper divisors (99347659).

688740661 is a wasteful number, since it uses less digits than its factorization.

688740661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119523.

The product of its (nonzero) digits is 387072, while the sum is 46.

The square root of 688740661 is about 26243.8690173534. The cubic root of 688740661 is about 883.1176697033.

The spelling of 688740661 in words is "six hundred eighty-eight million, seven hundred forty thousand, six hundred sixty-one".