691780986 has 40 divisors (see below), whose sum is σ = 1669345524. Its totient is φ = 212855040.

The previous prime is 691780979. The next prime is 691781003. The reversal of 691780986 is 689087196.

It can be written as a sum of positive squares in 2 ways, for example, as 653773761 + 38007225 = 25569^2 + 6165^2 .

It is a super-2 number, since 2×691780986² = 957121865182264392, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 162135 + ... + 166346.

Almost surely, 2^691780986 is an apocalyptic number.

691780986 is an abundant number, since it is smaller than the sum of its proper divisors (977564538).

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

691780986 is a wasteful number, since it uses less digits than its factorization.

691780986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328508 (or 328499 counting only the distinct ones).

The product of its (nonzero) digits is 1306368, while the sum is 54.

The square root of 691780986 is about 26301.7297149826. The cubic root of 691780986 is about 884.4152183901.

The spelling of 691780986 in words is "six hundred ninety-one million, seven hundred eighty thousand, nine hundred eighty-six".