721171261 has 4 divisors (see below), whose sum is σ = 721283292. Its totient is φ = 721059232.

The previous prime is 721171247. The next prime is 721171273. The reversal of 721171261 is 162171127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 162171127 = 83 ⋅1953869.

It can be written as a sum of positive squares in 2 ways, for example, as 57851236 + 663320025 = 7606^2 + 25755^2 .

It is a cyclic number.

It is not a de Polignac number, because 721171261 - 2¹⁵ = 721138493 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 (721171861) 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, 45730 + ... + 59443.

It is an arithmetic number, because the mean of its divisors is an integer number (180320823).

Almost surely, 2^721171261 is an apocalyptic number.

It is an amenable number.

721171261 is a deficient number, since it is larger than the sum of its proper divisors (112031).

721171261 is a wasteful number, since it uses less digits than its factorization.

721171261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112030.

The product of its digits is 1176, while the sum is 28.

The square root of 721171261 is about 26854.6320213106. The cubic root of 721171261 is about 896.7666947706.

The spelling of 721171261 in words is "seven hundred twenty-one million, one hundred seventy-one thousand, two hundred sixty-one".