221212021 has 2 divisors, whose sum is σ = 221212022. Its totient is φ = 221212020.

The previous prime is 221212009. The next prime is 221212031. The reversal of 221212021 is 120212122.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 118919025 + 102292996 = 10905^2 + 10114^2 .

It is a cyclic number.

It is not a de Polignac number, because 221212021 - 2⁵ = 221211989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 221211992 and 221212010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221212031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110606010 + 110606011.

It is an arithmetic number, because the mean of its divisors is an integer number (110606011).

Almost surely, 2^221212021 is an apocalyptic number.

It is an amenable number.

221212021 is a deficient number, since it is larger than the sum of its proper divisors (1).

221212021 is an equidigital number, since it uses as much as digits as its factorization.

221212021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 221212021 is about 14873.1980757334. The cubic root of 221212021 is about 604.7876412448.

Adding to 221212021 its reverse (120212122), we get a palindrome (341424143).

It can be divided in two parts, 22121 and 2021, that added together give a palindrome (24142).

The spelling of 221212021 in words is "two hundred twenty-one million, two hundred twelve thousand, twenty-one".