681256021 has 8 divisors (see below), whose sum is σ = 712347264. Its totient is φ = 650287440.

The previous prime is 681256019. The next prime is 681256057. The reversal of 681256021 is 120652186.

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 681256021 - 2¹ = 681256019 is a prime.

It is a super-2 number, since 2×681256021² = 928219532297504882, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681256061) 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 7 ways as a sum of consecutive naturals, for example, 19210 + ... + 41611.

It is an arithmetic number, because the mean of its divisors is an integer number (89043408).

Almost surely, 2^681256021 is an apocalyptic number.

It is an amenable number.

681256021 is a deficient number, since it is larger than the sum of its proper divisors (31091243).

681256021 is a wasteful number, since it uses less digits than its factorization.

681256021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61331.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 681256021 is about 26100.8816134628. The cubic root of 681256021 is about 879.9070240097.

The spelling of 681256021 in words is "six hundred eighty-one million, two hundred fifty-six thousand, twenty-one".