221657421 has 4 divisors (see below), whose sum is σ = 295543232. Its totient is φ = 147771612.

The previous prime is 221657383. The next prime is 221657453. The reversal of 221657421 is 124756122.

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 221657421 - 2⁹ = 221656909 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 (221657221) 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, 36942901 + ... + 36942906.

It is an arithmetic number, because the mean of its divisors is an integer number (73885808).

Almost surely, 2^221657421 is an apocalyptic number.

It is an amenable number.

221657421 is a deficient number, since it is larger than the sum of its proper divisors (73885811).

221657421 is an equidigital number, since it uses as much as digits as its factorization.

221657421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73885810.

The product of its digits is 6720, while the sum is 30.

The square root of 221657421 is about 14888.1637887283. The cubic root of 221657421 is about 605.1932729499.

The spelling of 221657421 in words is "two hundred twenty-one million, six hundred fifty-seven thousand, four hundred twenty-one".