21603539 has 2 divisors, whose sum is σ = 21603540. Its totient is φ = 21603538.

The previous prime is 21603511. The next prime is 21603541. The reversal of 21603539 is 93530612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21603539 - 2¹² = 21599443 is a prime.

Together with 21603541, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21603599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10801769 + 10801770.

It is an arithmetic number, because the mean of its divisors is an integer number (10801770).

Almost surely, 2^21603539 is an apocalyptic number.

21603539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21603539 is an equidigital number, since it uses as much as digits as its factorization.

21603539 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21603539 is about 4647.9607356345. The cubic root of 21603539 is about 278.5105389851.

The spelling of 21603539 in words is "twenty-one million, six hundred three thousand, five hundred thirty-nine".