721731251 has 4 divisors (see below), whose sum is σ = 721999992. Its totient is φ = 721462512.

The previous prime is 721731233. The next prime is 721731253. The reversal of 721731251 is 152137127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 152137127 = 349 ⋅435923.

It is a cyclic number.

It is not a de Polignac number, because 721731251 - 2⁶ = 721731187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721731253) 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, 130301 + ... + 135726.

It is an arithmetic number, because the mean of its divisors is an integer number (180499998).

Almost surely, 2^721731251 is an apocalyptic number.

721731251 is a deficient number, since it is larger than the sum of its proper divisors (268741).

721731251 is a wasteful number, since it uses less digits than its factorization.

721731251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268740.

The product of its digits is 2940, while the sum is 29.

The square root of 721731251 is about 26865.0563185712. The cubic root of 721731251 is about 896.9987480444.

Adding to 721731251 its reverse (152137127), we get a palindrome (873868378).

The spelling of 721731251 in words is "seven hundred twenty-one million, seven hundred thirty-one thousand, two hundred fifty-one".