681728421 has 32 divisors (see below), whose sum is σ = 1012377600. Its totient is φ = 404570880.

The previous prime is 681728393. The next prime is 681728449. The reversal of 681728421 is 124827186.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (681728393) and next prime (681728449).

It is not a de Polignac number, because 681728421 - 2⁵ = 681728389 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 681728421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681728221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 655620 + ... + 656658.

It is an arithmetic number, because the mean of its divisors is an integer number (31636800).

Almost surely, 2^681728421 is an apocalyptic number.

It is an amenable number.

681728421 is a deficient number, since it is larger than the sum of its proper divisors (330649179).

681728421 is a wasteful number, since it uses less digits than its factorization.

681728421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1449.

The product of its digits is 43008, while the sum is 39.

The square root of 681728421 is about 26109.9295479708. The cubic root of 681728421 is about 880.1103602123.

The spelling of 681728421 in words is "six hundred eighty-one million, seven hundred twenty-eight thousand, four hundred twenty-one".