681246721 has 4 divisors (see below), whose sum is σ = 697089712. Its totient is φ = 665403732.

The previous prime is 681246697. The next prime is 681246751. The reversal of 681246721 is 127642186.

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 681246721 - 2⁵ = 681246689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (681246751) 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, 7921431 + ... + 7921516.

It is an arithmetic number, because the mean of its divisors is an integer number (174272428).

It is a Proth number, since it is equal to 10395 ⋅ 2¹⁶ + 1 and 10395 < 2¹⁶.

Almost surely, 2^681246721 is an apocalyptic number.

It is an amenable number.

681246721 is a deficient number, since it is larger than the sum of its proper divisors (15842991).

681246721 is a wasteful number, since it uses less digits than its factorization.

681246721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15842990.

The product of its digits is 32256, while the sum is 37.

The square root of 681246721 is about 26100.7034579530. The cubic root of 681246721 is about 879.9030200462.

The spelling of 681246721 in words is "six hundred eighty-one million, two hundred forty-six thousand, seven hundred twenty-one".