21185123 has 2 divisors, whose sum is σ = 21185124. Its totient is φ = 21185122.

The previous prime is 21185113. The next prime is 21185173. The reversal of 21185123 is 32158112.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21185123 - 2¹⁰ = 21184099 is a prime.

It is not a weakly prime, because it can be changed into another prime (21185113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10592561 + 10592562.

It is an arithmetic number, because the mean of its divisors is an integer number (10592562).

Almost surely, 2^21185123 is an apocalyptic number.

21185123 is a deficient number, since it is larger than the sum of its proper divisors (1).

21185123 is an equidigital number, since it uses as much as digits as its factorization.

21185123 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 23.

The square root of 21185123 is about 4602.7299508009. The cubic root of 21185123 is about 276.7007459512.

It can be divided in two parts, 2118512 and 3, that multiplied together give a palindrome (6355536).

The spelling of 21185123 in words is "twenty-one million, one hundred eighty-five thousand, one hundred twenty-three".