688991780 has 12 divisors (see below), whose sum is σ = 1446882780. Its totient is φ = 275596704.

The previous prime is 688991777. The next prime is 688991783. The reversal of 688991780 is 87199886.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (688991777) and next prime (688991783).

It can be written as a sum of positive squares in 2 ways, for example, as 159163456 + 529828324 = 12616^2 + 23018^2 .

It is not an unprimeable number, because it can be changed into a prime (688991783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17224775 + ... + 17224814.

It is an arithmetic number, because the mean of its divisors is an integer number (120573565).

Almost surely, 2^688991780 is an apocalyptic number.

It is an amenable number.

688991780 is an abundant number, since it is smaller than the sum of its proper divisors (757891000).

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

688991780 is a wasteful number, since it uses less digits than its factorization.

688991780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34449598 (or 34449596 counting only the distinct ones).

The product of its (nonzero) digits is 1741824, while the sum is 56.

The square root of 688991780 is about 26248.6529178166. The cubic root of 688991780 is about 883.2249866716.

The spelling of 688991780 in words is "six hundred eighty-eight million, nine hundred ninety-one thousand, seven hundred eighty".