221540021 has 2 divisors, whose sum is σ = 221540022. Its totient is φ = 221540020.

The previous prime is 221540017. The next prime is 221540027. The reversal of 221540021 is 120045122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 188073796 + 33466225 = 13714^2 + 5785^2 .

It is a cyclic number.

It is not a de Polignac number, because 221540021 - 2² = 221540017 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 (221540027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110770010 + 110770011.

It is an arithmetic number, because the mean of its divisors is an integer number (110770011).

Almost surely, 2^221540021 is an apocalyptic number.

It is an amenable number.

221540021 is a deficient number, since it is larger than the sum of its proper divisors (1).

221540021 is an equidigital number, since it uses as much as digits as its factorization.

221540021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 221540021 is about 14884.2205371998. The cubic root of 221540021 is about 605.0864079848.

Adding to 221540021 its reverse (120045122), we get a palindrome (341585143).

The spelling of 221540021 in words is "two hundred twenty-one million, five hundred forty thousand, twenty-one".