21123013 has 2 divisors, whose sum is σ = 21123014. Its totient is φ = 21123012.

The previous prime is 21122971. The next prime is 21123017. The reversal of 21123013 is 31032112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10870209 + 10252804 = 3297^2 + 3202^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21122984 and 21123002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561506 + 10561507.

It is an arithmetic number, because the mean of its divisors is an integer number (10561507).

Almost surely, 2^21123013 is an apocalyptic number.

It is an amenable number.

21123013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123013 is an equidigital number, since it uses as much as digits as its factorization.

21123013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21123013 is about 4595.9779155257. The cubic root of 21123013 is about 276.4300732125.

Adding to 21123013 its reverse (31032112), we get a palindrome (52155125).

Subtracting 21123013 from its reverse (31032112), we obtain a palindrome (9909099).

The spelling of 21123013 in words is "twenty-one million, one hundred twenty-three thousand, thirteen".