681521281 has 4 divisors (see below), whose sum is σ = 778881472. Its totient is φ = 584161092.

The previous prime is 681521251. The next prime is 681521297. The reversal of 681521281 is 182125186.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 681521281 - 2¹³ = 681513089 is a prime.

It is a super-2 number, since 2×681521281² = 928942512911761922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (681521201) 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, 48680085 + ... + 48680098.

It is an arithmetic number, because the mean of its divisors is an integer number (194720368).

Almost surely, 2^681521281 is an apocalyptic number.

It is an amenable number.

681521281 is a deficient number, since it is larger than the sum of its proper divisors (97360191).

681521281 is an equidigital number, since it uses as much as digits as its factorization.

681521281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97360190.

The product of its digits is 7680, while the sum is 34.

The square root of 681521281 is about 26105.9625564736. The cubic root of 681521281 is about 880.0212120403.

The spelling of 681521281 in words is "six hundred eighty-one million, five hundred twenty-one thousand, two hundred eighty-one".