21185539 has 2 divisors, whose sum is σ = 21185540. Its totient is φ = 21185538.

The previous prime is 21185537. The next prime is 21185557. The reversal of 21185539 is 93558112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21185539 - 2¹ = 21185537 is a prime.

Together with 21185537, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21185533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10592769 + 10592770.

It is an arithmetic number, because the mean of its divisors is an integer number (10592770).

Almost surely, 2^21185539 is an apocalyptic number.

21185539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21185539 is an equidigital number, since it uses as much as digits as its factorization.

21185539 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10800, while the sum is 34.

The square root of 21185539 is about 4602.7751411513. The cubic root of 21185539 is about 276.7025570768.

The spelling of 21185539 in words is "twenty-one million, one hundred eighty-five thousand, five hundred thirty-nine".