20390221 has 2 divisors, whose sum is σ = 20390222. Its totient is φ = 20390220.

The previous prime is 20390207. The next prime is 20390239. The reversal of 20390221 is 12209302.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12888100 + 7502121 = 3590^2 + 2739^2 .

It is a cyclic number.

It is not a de Polignac number, because 20390221 - 2¹³ = 20382029 is a prime.

It is a super-2 number, since 2×20390221² = 831522224857682, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20390261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10195110 + 10195111.

It is an arithmetic number, because the mean of its divisors is an integer number (10195111).

Almost surely, 2^20390221 is an apocalyptic number.

It is an amenable number.

20390221 is a deficient number, since it is larger than the sum of its proper divisors (1).

20390221 is an equidigital number, since it uses as much as digits as its factorization.

20390221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 20390221 is about 4515.5532329937. The cubic root of 20390221 is about 273.1957743616.

Adding to 20390221 its reverse (12209302), we get a palindrome (32599523).

The spelling of 20390221 in words is "twenty million, three hundred ninety thousand, two hundred twenty-one".