20401021 has 2 divisors, whose sum is σ = 20401022. Its totient is φ = 20401020.

The previous prime is 20401013. The next prime is 20401033. The reversal of 20401021 is 12010402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16695396 + 3705625 = 4086^2 + 1925^2 .

It is a cyclic number.

It is not a de Polignac number, because 20401021 - 2³ = 20401013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20400989 and 20401007.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20401001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10200510 + 10200511.

It is an arithmetic number, because the mean of its divisors is an integer number (10200511).

Almost surely, 2^20401021 is an apocalyptic number.

It is an amenable number.

20401021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20401021 is an equidigital number, since it uses as much as digits as its factorization.

20401021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 20401021 is about 4516.7489414401. The cubic root of 20401021 is about 273.2439999888.

Adding to 20401021 its reverse (12010402), we get a palindrome (32411423).

The spelling of 20401021 in words is "twenty million, four hundred one thousand, twenty-one".