721646121 has 32 divisors (see below), whose sum is σ = 1139731200. Its totient is φ = 397867008.

The previous prime is 721646083. The next prime is 721646129. The reversal of 721646121 is 121646127.

It is not a de Polignac number, because 721646121 - 2⁹ = 721645609 is a prime.

It is not an unprimeable number, because it can be changed into a prime (721646129) 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, 511465 + ... + 512873.

It is an arithmetic number, because the mean of its divisors is an integer number (35616600).

Almost surely, 2^721646121 is an apocalyptic number.

It is an amenable number.

721646121 is a deficient number, since it is larger than the sum of its proper divisors (418085079).

721646121 is an equidigital number, since it uses as much as digits as its factorization.

721646121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1506 (or 1448 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 721646121 is about 26863.4718716699. The cubic root of 721646121 is about 896.9634789116.

The spelling of 721646121 in words is "seven hundred twenty-one million, six hundred forty-six thousand, one hundred twenty-one".