21745613 has 2 divisors, whose sum is σ = 21745614. Its totient is φ = 21745612.

The previous prime is 21745579. The next prime is 21745627. The reversal of 21745613 is 31654712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15976009 + 5769604 = 3997^2 + 2402^2 .

It is a cyclic number.

It is not a de Polignac number, because 21745613 - 2⁸ = 21745357 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21745643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10872806 + 10872807.

It is an arithmetic number, because the mean of its divisors is an integer number (10872807).

Almost surely, 2^21745613 is an apocalyptic number.

It is an amenable number.

21745613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21745613 is an equidigital number, since it uses as much as digits as its factorization.

21745613 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 29.

The square root of 21745613 is about 4663.2191670562. The cubic root of 21745613 is about 279.1197398016.

Subtracting 21745613 from its reverse (31654712), we obtain a palindrome (9909099).

The spelling of 21745613 in words is "twenty-one million, seven hundred forty-five thousand, six hundred thirteen".