221428997 has 2 divisors, whose sum is σ = 221428998. Its totient is φ = 221428996.

The previous prime is 221428913. The next prime is 221429041. The reversal of 221428997 is 799824122.

221428997 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (221429041) can be obtained adding 221428997 to its sum of digits (44).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 170720356 + 50708641 = 13066^2 + 7121^2 .

It is a cyclic number.

It is not a de Polignac number, because 221428997 - 2²⁰ = 220380421 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221428297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110714498 + 110714499.

It is an arithmetic number, because the mean of its divisors is an integer number (110714499).

Almost surely, 2^221428997 is an apocalyptic number.

It is an amenable number.

221428997 is a deficient number, since it is larger than the sum of its proper divisors (1).

221428997 is an equidigital number, since it uses as much as digits as its factorization.

221428997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 44.

The square root of 221428997 is about 14880.4904825076. The cubic root of 221428997 is about 604.9853121221.

The spelling of 221428997 in words is "two hundred twenty-one million, four hundred twenty-eight thousand, nine hundred ninety-seven".