721551261 has 4 divisors (see below), whose sum is σ = 962068352. Its totient is φ = 481034172.

The previous prime is 721551253. The next prime is 721551263. The reversal of 721551261 is 162155127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 721551261 - 2³ = 721551253 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 (721551263) 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, 120258541 + ... + 120258546.

It is an arithmetic number, because the mean of its divisors is an integer number (240517088).

Almost surely, 2^721551261 is an apocalyptic number.

It is an amenable number.

721551261 is a deficient number, since it is larger than the sum of its proper divisors (240517091).

721551261 is a wasteful number, since it uses less digits than its factorization.

721551261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240517090.

The product of its digits is 4200, while the sum is 30.

The square root of 721551261 is about 26861.7062190770. The cubic root of 721551261 is about 896.9241753982.

It can be divided in two parts, 72155126 and 1, that added together give a palindrome (72155127).

The spelling of 721551261 in words is "seven hundred twenty-one million, five hundred fifty-one thousand, two hundred sixty-one".