221329991 has 2 divisors, whose sum is σ = 221329992. Its totient is φ = 221329990.

The previous prime is 221329981. The next prime is 221330047. The reversal of 221329991 is 199923122.

221329991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221329991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221329951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110664995 + 110664996.

It is an arithmetic number, because the mean of its divisors is an integer number (110664996).

Almost surely, 2^221329991 is an apocalyptic number.

221329991 is a deficient number, since it is larger than the sum of its proper divisors (1).

221329991 is an equidigital number, since it uses as much as digits as its factorization.

221329991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17496, while the sum is 38.

The square root of 221329991 is about 14877.1634057034. The cubic root of 221329991 is about 604.8951310618.

It can be divided in two parts, 22132 and 9991, that added together give a palindrome (32123).

The spelling of 221329991 in words is "two hundred twenty-one million, three hundred twenty-nine thousand, nine hundred ninety-one".