1309725221 has 4 divisors (see below), whose sum is σ = 1496828832. Its totient is φ = 1122621612.

The previous prime is 1309725211. The next prime is 1309725229. The reversal of 1309725221 is 1225279031.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1225279031 = 499 ⋅2455469.

It is not a de Polignac number, because 1309725221 - 2²⁶ = 1242616357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1309725229) 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, 93551795 + ... + 93551808.

It is an arithmetic number, because the mean of its divisors is an integer number (374207208).

Almost surely, 2^1309725221 is an apocalyptic number.

It is an amenable number.

1309725221 is a deficient number, since it is larger than the sum of its proper divisors (187103611).

1309725221 is an equidigital number, since it uses as much as digits as its factorization.

1309725221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187103610.

The product of its (nonzero) digits is 7560, while the sum is 32.

The square root of 1309725221 is about 36190.1260152545. The cubic root of 1309725221 is about 1094.1076724935.

The spelling of 1309725221 in words is "one billion, three hundred nine million, seven hundred twenty-five thousand, two hundred twenty-one".