221431921 has 2 divisors, whose sum is σ = 221431922. Its totient is φ = 221431920.

The previous prime is 221431913. The next prime is 221431943. The reversal of 221431921 is 129134122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 177023025 + 44408896 = 13305^2 + 6664^2 .

It is a cyclic number.

It is not a de Polignac number, because 221431921 - 2³ = 221431913 is a prime.

It is not a weakly prime, because it can be changed into another prime (221431901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110715960 + 110715961.

It is an arithmetic number, because the mean of its divisors is an integer number (110715961).

Almost surely, 2^221431921 is an apocalyptic number.

It is an amenable number.

221431921 is a deficient number, since it is larger than the sum of its proper divisors (1).

221431921 is an equidigital number, since it uses as much as digits as its factorization.

221431921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 25.

The square root of 221431921 is about 14880.5887316329. The cubic root of 221431921 is about 604.9879750814.

The spelling of 221431921 in words is "two hundred twenty-one million, four hundred thirty-one thousand, nine hundred twenty-one".