21259913 has 2 divisors, whose sum is σ = 21259914. Its totient is φ = 21259912.

The previous prime is 21259897. The next prime is 21259919. The reversal of 21259913 is 31995212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19998784 + 1261129 = 4472^2 + 1123^2 .

It is a cyclic number.

It is not a de Polignac number, because 21259913 - 2⁴ = 21259897 is a prime.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21259913.

It is not a weakly prime, because it can be changed into another prime (21259919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10629956 + 10629957.

It is an arithmetic number, because the mean of its divisors is an integer number (10629957).

Almost surely, 2^21259913 is an apocalyptic number.

It is an amenable number.

21259913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21259913 is an equidigital number, since it uses as much as digits as its factorization.

21259913 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4860, while the sum is 32.

The square root of 21259913 is about 4610.8473190944. The cubic root of 21259913 is about 277.0259764420.

The spelling of 21259913 in words is "twenty-one million, two hundred fifty-nine thousand, nine hundred thirteen".