21912123 has 16 divisors (see below), whose sum is σ = 30594816. Its totient is φ = 13923360.

The previous prime is 21912101. The next prime is 21912157. The reversal of 21912123 is 32121912.

It is not a de Polignac number, because 21912123 - 2⁹ = 21911611 is a prime.

It is a super-2 number, since 2×21912123² = 960282268734258, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21912123.

It is not an unprimeable number, because it can be changed into a prime (21912173) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37036 + ... + 37622.

It is an arithmetic number, because the mean of its divisors is an integer number (1912176).

Almost surely, 2^21912123 is an apocalyptic number.

21912123 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21912123 is a deficient number, since it is larger than the sum of its proper divisors (8682693).

21912123 is a wasteful number, since it uses less digits than its factorization.

With its predecessor (21912122) it forms an eRAP, since the sums of their prime factors are consecutive (1153 and 1154).

21912123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1154.

The product of its digits is 216, while the sum is 21.

The square root of 21912123 is about 4681.0386667918. The cubic root of 21912123 is about 279.8303521656.

The spelling of 21912123 in words is "twenty-one million, nine hundred twelve thousand, one hundred twenty-three".