681921691 has 8 divisors (see below), whose sum is σ = 757951344. Its totient is φ = 608231520.

The previous prime is 681921683. The next prime is 681921719. The reversal of 681921691 is 196129186.

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 681921691 - 2³ = 681921683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (681921661) 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, 584256 + ... + 585421.

It is an arithmetic number, because the mean of its divisors is an integer number (94743918).

Almost surely, 2^681921691 is an apocalyptic number.

681921691 is a deficient number, since it is larger than the sum of its proper divisors (76029653).

681921691 is a wasteful number, since it uses less digits than its factorization.

681921691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1169741.

The product of its digits is 46656, while the sum is 43.

The square root of 681921691 is about 26113.6303680664. The cubic root of 681921691 is about 880.1935227798.

The spelling of 681921691 in words is "six hundred eighty-one million, nine hundred twenty-one thousand, six hundred ninety-one".