21820013 has 2 divisors, whose sum is σ = 21820014. Its totient is φ = 21820012.

The previous prime is 21819991. The next prime is 21820033. The reversal of 21820013 is 31002812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19518724 + 2301289 = 4418^2 + 1517^2 .

It is a cyclic number.

It is not a de Polignac number, because 21820013 - 2⁶ = 21819949 is a prime.

It is a super-2 number, since 2×21820013² = 952225934640338, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21819973 and 21820000.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21820033) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10910006 + 10910007.

It is an arithmetic number, because the mean of its divisors is an integer number (10910007).

Almost surely, 2^21820013 is an apocalyptic number.

It is an amenable number.

21820013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21820013 is an equidigital number, since it uses as much as digits as its factorization.

21820013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 21820013 is about 4671.1896771593. The cubic root of 21820013 is about 279.4377023287.

Adding to 21820013 its reverse (31002812), we get a palindrome (52822825).

The spelling of 21820013 in words is "twenty-one million, eight hundred twenty thousand, thirteen".