721428646 has 4 divisors (see below), whose sum is σ = 1082142972. Its totient is φ = 360714322.

The previous prime is 721428637. The next prime is 721428667. The reversal of 721428646 is 646824127.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 646824127 = 419 ⋅1543733.

It is a junction number, because it is equal to n+sod(n) for n = 721428599 and 721428608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 180357160 + ... + 180357163.

It is an arithmetic number, because the mean of its divisors is an integer number (270535743).

Almost surely, 2^721428646 is an apocalyptic number.

721428646 is a deficient number, since it is larger than the sum of its proper divisors (360714326).

721428646 is a wasteful number, since it uses less digits than its factorization.

721428646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360714325.

The product of its digits is 129024, while the sum is 40.

The square root of 721428646 is about 26859.4237838417. The cubic root of 721428646 is about 896.8733670016.

The spelling of 721428646 in words is "seven hundred twenty-one million, four hundred twenty-eight thousand, six hundred forty-six".