221957409 has 4 divisors (see below), whose sum is σ = 295943216. Its totient is φ = 147971604.

The previous prime is 221957381. The next prime is 221957459. The reversal of 221957409 is 904759122.

221957409 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 a de Polignac number, because none of the positive numbers 2^k-221957409 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (221957459) 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, 36992899 + ... + 36992904.

It is an arithmetic number, because the mean of its divisors is an integer number (73985804).

Almost surely, 2^221957409 is an apocalyptic number.

It is an amenable number.

221957409 is a deficient number, since it is larger than the sum of its proper divisors (73985807).

221957409 is an equidigital number, since it uses as much as digits as its factorization.

221957409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73985806.

The product of its (nonzero) digits is 45360, while the sum is 39.

The square root of 221957409 is about 14898.2350968160. The cubic root of 221957409 is about 605.4661698638.

The spelling of 221957409 in words is "two hundred twenty-one million, nine hundred fifty-seven thousand, four hundred nine".