681980921 has 4 divisors (see below), whose sum is σ = 698614644. Its totient is φ = 665347200.

The previous prime is 681980917. The next prime is 681980939. The reversal of 681980921 is 129089186.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 275394025 + 406586896 = 16595^2 + 20164^2 .

It is a cyclic number.

It is not a de Polignac number, because 681980921 - 2² = 681980917 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (681980911) 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, 8316800 + ... + 8316881.

It is an arithmetic number, because the mean of its divisors is an integer number (174653661).

Almost surely, 2^681980921 is an apocalyptic number.

It is an amenable number.

681980921 is a deficient number, since it is larger than the sum of its proper divisors (16633723).

681980921 is a wasteful number, since it uses less digits than its factorization.

681980921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16633722.

The product of its (nonzero) digits is 62208, while the sum is 44.

The square root of 681980921 is about 26114.7644255122. The cubic root of 681980921 is about 880.2190058392.

The spelling of 681980921 in words is "six hundred eighty-one million, nine hundred eighty thousand, nine hundred twenty-one".