21603613 has 2 divisors, whose sum is σ = 21603614. Its totient is φ = 21603612.

The previous prime is 21603607. The next prime is 21603643. The reversal of 21603613 is 31630612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14002564 + 7601049 = 3742^2 + 2757^2 .

It is a cyclic number.

It is not a de Polignac number, because 21603613 - 2⁵ = 21603581 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21603643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10801806 + 10801807.

It is an arithmetic number, because the mean of its divisors is an integer number (10801807).

Almost surely, 2^21603613 is an apocalyptic number.

It is an amenable number.

21603613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21603613 is an equidigital number, since it uses as much as digits as its factorization.

21603613 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 21603613 is about 4647.9686961080. The cubic root of 21603613 is about 278.5108569848.

The spelling of 21603613 in words is "twenty-one million, six hundred three thousand, six hundred thirteen".