721642531 has 4 divisors (see below), whose sum is σ = 723077712. Its totient is φ = 720207352.

The previous prime is 721642529. The next prime is 721642567. The reversal of 721642531 is 135246127.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 721642531 - 2¹ = 721642529 is a prime.

It is a super-2 number, since 2×721642531² = 1041535885096171922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 721642493 and 721642502.

It is not an unprimeable number, because it can be changed into a prime (721642501) 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, 716836 + ... + 717841.

It is an arithmetic number, because the mean of its divisors is an integer number (180769428).

Almost surely, 2^721642531 is an apocalyptic number.

721642531 is a deficient number, since it is larger than the sum of its proper divisors (1435181).

721642531 is a wasteful number, since it uses less digits than its factorization.

721642531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1435180.

The product of its digits is 10080, while the sum is 31.

The square root of 721642531 is about 26863.4050522267. The cubic root of 721642531 is about 896.9619915232.

Adding to 721642531 its reverse (135246127), we get a palindrome (856888658).

The spelling of 721642531 in words is "seven hundred twenty-one million, six hundred forty-two thousand, five hundred thirty-one".