21185387 has 2 divisors, whose sum is σ = 21185388. Its totient is φ = 21185386.

The previous prime is 21185377. The next prime is 21185389. The reversal of 21185387 is 78358112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21185387 - 2⁴ = 21185371 is a prime.

Together with 21185389, 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 (21185389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10592693 + 10592694.

It is an arithmetic number, because the mean of its divisors is an integer number (10592694).

Almost surely, 2^21185387 is an apocalyptic number.

21185387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21185387 is an equidigital number, since it uses as much as digits as its factorization.

21185387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13440, while the sum is 35.

The square root of 21185387 is about 4602.7586293439. The cubic root of 21185387 is about 276.7018953221.

The spelling of 21185387 in words is "twenty-one million, one hundred eighty-five thousand, three hundred eighty-seven".