228220021 has 2 divisors, whose sum is σ = 228220022. Its totient is φ = 228220020.

The previous prime is 228220009. The next prime is 228220061. The reversal of 228220021 is 120022822.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204347025 + 23872996 = 14295^2 + 4886^2 .

It is a cyclic number.

It is not a de Polignac number, because 228220021 - 2⁵ = 228219989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (228220061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 114110010 + 114110011.

It is an arithmetic number, because the mean of its divisors is an integer number (114110011).

Almost surely, 2^228220021 is an apocalyptic number.

It is an amenable number.

228220021 is a deficient number, since it is larger than the sum of its proper divisors (1).

228220021 is an equidigital number, since it uses as much as digits as its factorization.

228220021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 228220021 is about 15106.9527370678. The cubic root of 228220021 is about 611.1079220023.

Adding to 228220021 its reverse (120022822), we get a palindrome (348242843).

The spelling of 228220021 in words is "two hundred twenty-eight million, two hundred twenty thousand, twenty-one".