691880781 has 8 divisors (see below), whose sum is σ = 945008064. Its totient is φ = 450003680.

The previous prime is 691880771. The next prime is 691880821. The reversal of 691880781 is 187088196.

691880781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 691880781 - 2¹³ = 691872589 is a prime.

It is a super-2 number, since 2×691880781² = 957398030234339922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 691880781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691880711) 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, 2812401 + ... + 2812646.

It is an arithmetic number, because the mean of its divisors is an integer number (118126008).

Almost surely, 2^691880781 is an apocalyptic number.

It is an amenable number.

691880781 is a deficient number, since it is larger than the sum of its proper divisors (253127283).

691880781 is a wasteful number, since it uses less digits than its factorization.

691880781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5625091.

The product of its (nonzero) digits is 193536, while the sum is 48.

The square root of 691880781 is about 26303.6267651440. The cubic root of 691880781 is about 884.4577443604.

The spelling of 691880781 in words is "six hundred ninety-one million, eight hundred eighty thousand, seven hundred eighty-one".