221621431 has 4 divisors (see below), whose sum is σ = 222541264. Its totient is φ = 220701600.

The previous prime is 221621293. The next prime is 221621437. The reversal of 221621431 is 134126122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221621431 - 2¹⁷ = 221490359 is a prime.

It is a super-2 number, since 2×221621431² = 98232117356975522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221621437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 459555 + ... + 460036.

It is an arithmetic number, because the mean of its divisors is an integer number (55635316).

Almost surely, 2^221621431 is an apocalyptic number.

221621431 is a deficient number, since it is larger than the sum of its proper divisors (919833).

221621431 is an equidigital number, since it uses as much as digits as its factorization.

221621431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 919832.

The product of its digits is 576, while the sum is 22.

The square root of 221621431 is about 14886.9550613952. The cubic root of 221621431 is about 605.1605165689.

Adding to 221621431 its reverse (134126122), we get a palindrome (355747553).

The spelling of 221621431 in words is "two hundred twenty-one million, six hundred twenty-one thousand, four hundred thirty-one".