20421013 has 2 divisors, whose sum is σ = 20421014. Its totient is φ = 20421012.

The previous prime is 20420999. The next prime is 20421043. The reversal of 20421013 is 31012402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17918289 + 2502724 = 4233^2 + 1582^2 .

It is a cyclic number.

It is not a de Polignac number, because 20421013 - 2²¹ = 18323861 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20420984 and 20421002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20421043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10210506 + 10210507.

It is an arithmetic number, because the mean of its divisors is an integer number (10210507).

Almost surely, 2^20421013 is an apocalyptic number.

It is an amenable number.

20421013 is a deficient number, since it is larger than the sum of its proper divisors (1).

20421013 is an equidigital number, since it uses as much as digits as its factorization.

20421013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 20421013 is about 4518.9614957421. The cubic root of 20421013 is about 273.3332260889. Note that the first 3 decimals are identical.

Adding to 20421013 its reverse (31012402), we get a palindrome (51433415).

The spelling of 20421013 in words is "twenty million, four hundred twenty-one thousand, thirteen".