681749397 has 18 divisors (see below), whose sum is σ = 1145525238. Its totient is φ = 389570832.

The previous prime is 681749377. The next prime is 681749413. The reversal of 681749397 is 793947186.

It is a happy number.

681749397 is a `hidden beast` number, since 68 + 1 + 7 + 493 + 97 = 666.

It can be written as a sum of positive squares in only one way, i.e., 574129521 + 107619876 = 23961^2 + 10374^2 .

It is not a de Polignac number, because 681749397 - 2¹⁶ = 681683861 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681749347) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 772518 + ... + 773399.

It is an arithmetic number, because the mean of its divisors is an integer number (63640291).

Almost surely, 2^681749397 is an apocalyptic number.

It is an amenable number.

681749397 is a deficient number, since it is larger than the sum of its proper divisors (463775841).

681749397 is a wasteful number, since it uses less digits than its factorization.

681749397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1545937 (or 1545927 counting only the distinct ones).

The product of its digits is 2286144, while the sum is 54.

The square root of 681749397 is about 26110.3312311430. The cubic root of 681749397 is about 880.1193867811.

The spelling of 681749397 in words is "six hundred eighty-one million, seven hundred forty-nine thousand, three hundred ninety-seven".