721642247 has 4 divisors (see below), whose sum is σ = 725381520. Its totient is φ = 717902976.

The previous prime is 721642217. The next prime is 721642253. The reversal of 721642247 is 742246127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 742246127 = 7 ⋅106035161.

It is a cyclic number.

It is not a de Polignac number, because 721642247 - 2¹⁶ = 721576711 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721642217) 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 3 ways as a sum of consecutive naturals, for example, 1869347 + ... + 1869732.

It is an arithmetic number, because the mean of its divisors is an integer number (181345380).

Almost surely, 2^721642247 is an apocalyptic number.

721642247 is a deficient number, since it is larger than the sum of its proper divisors (3739273).

721642247 is a wasteful number, since it uses less digits than its factorization.

721642247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3739272.

The product of its digits is 37632, while the sum is 35.

The square root of 721642247 is about 26863.3997662247. The cubic root of 721642247 is about 896.9618738577.

The spelling of 721642247 in words is "seven hundred twenty-one million, six hundred forty-two thousand, two hundred forty-seven".