691290640 has 20 divisors (see below), whose sum is σ = 1607250924. Its totient is φ = 276516224.

The previous prime is 691290637. The next prime is 691290641. The reversal of 691290640 is 46092196.

It can be written as a sum of positive squares in 2 ways, for example, as 117592336 + 573698304 = 10844^2 + 23952^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a self number, because there is not a number n which added to its sum of digits gives 691290640.

It is not an unprimeable number, because it can be changed into a prime (691290641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4320487 + ... + 4320646.

Almost surely, 2^691290640 is an apocalyptic number.

It is an amenable number.

691290640 is an abundant number, since it is smaller than the sum of its proper divisors (915960284).

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

691290640 is a wasteful number, since it uses less digits than its factorization.

691290640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8641146 (or 8641140 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 691290640 is about 26292.4065083438. The cubic root of 691290640 is about 884.2062062038.

The spelling of 691290640 in words is "six hundred ninety-one million, two hundred ninety thousand, six hundred forty".