21125123 has 2 divisors, whose sum is σ = 21125124. Its totient is φ = 21125122.

The previous prime is 21125107. The next prime is 21125161. The reversal of 21125123 is 32152112.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21125123 - 2⁴ = 21125107 is a prime.

It is not a weakly prime, because it can be changed into another prime (21125183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562561 + 10562562.

It is an arithmetic number, because the mean of its divisors is an integer number (10562562).

Almost surely, 2^21125123 is an apocalyptic number.

21125123 is a deficient number, since it is larger than the sum of its proper divisors (1).

21125123 is an equidigital number, since it uses as much as digits as its factorization.

21125123 is an evil number, because the sum of its binary digits is even.

The product of its digits is 120, while the sum is 17.

The square root of 21125123 is about 4596.2074583291. The cubic root of 21125123 is about 276.4392772031.

Adding to 21125123 its reverse (32152112), we get a palindrome (53277235).

The spelling of 21125123 in words is "twenty-one million, one hundred twenty-five thousand, one hundred twenty-three".