20402021 has 2 divisors, whose sum is σ = 20402022. Its totient is φ = 20402020.

The previous prime is 20402017. The next prime is 20402087. The reversal of 20402021 is 12020402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20349121 + 52900 = 4511^2 + 230^2 .

It is a cyclic number.

It is not a de Polignac number, because 20402021 - 2² = 20402017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20401993 and 20402011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20402321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10201010 + 10201011.

It is an arithmetic number, because the mean of its divisors is an integer number (10201011).

Almost surely, 2^20402021 is an apocalyptic number.

It is an amenable number.

20402021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20402021 is an equidigital number, since it uses as much as digits as its factorization.

20402021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 11.

The square root of 20402021 is about 4516.8596391741. The cubic root of 20402021 is about 273.2484644636.

Adding to 20402021 its reverse (12020402), we get a palindrome (32422423).

The spelling of 20402021 in words is "twenty million, four hundred two thousand, twenty-one".