691658640 has 60 divisors (see below), whose sum is σ = 2322822684. Its totient is φ = 184442112.

The previous prime is 691658629. The next prime is 691658663. The reversal of 691658640 is 46856196.

691658640 is a `hidden beast` number, since 69 + 1 + 6 + 586 + 4 + 0 = 666.

691658640 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 233356176 + 458302464 = 15276^2 + 21408^2 .

It is a tau number, because it is divible by the number of its divisors (60).

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 11 ways as a sum of consecutive naturals, for example, 479599 + ... + 481038.

Almost surely, 2^691658640 is an apocalyptic number.

691658640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

691658640 is an abundant number, since it is smaller than the sum of its proper divisors (1631164044).

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

691658640 is a wasteful number, since it uses less digits than its factorization.

691658640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 960656 (or 960647 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The square root of 691658640 is about 26299.4037955236. The cubic root of 691658640 is about 884.3630771075.

It can be divided in two parts, 6916 and 58640, that added together give a palindrome (65556).

The spelling of 691658640 in words is "six hundred ninety-one million, six hundred fifty-eight thousand, six hundred forty".