721842391 has 4 divisors (see below), whose sum is σ = 723809632. Its totient is φ = 719875152.

The previous prime is 721842353. The next prime is 721842413. The reversal of 721842391 is 193248127.

721842391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 193248127 = 9929 ⋅19463.

It is a cyclic number.

It is not a de Polignac number, because 721842391 - 2²⁷ = 587624663 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721842391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721842311) 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, 983070 + ... + 983803.

It is an arithmetic number, because the mean of its divisors is an integer number (180952408).

Almost surely, 2^721842391 is an apocalyptic number.

721842391 is a deficient number, since it is larger than the sum of its proper divisors (1967241).

721842391 is a wasteful number, since it uses less digits than its factorization.

721842391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1967240.

The product of its digits is 24192, while the sum is 37.

The square root of 721842391 is about 26867.1247252102. The cubic root of 721842391 is about 897.0447888774.

The spelling of 721842391 in words is "seven hundred twenty-one million, eight hundred forty-two thousand, three hundred ninety-one".