21400123 has 4 divisors (see below), whose sum is σ = 21468808. Its totient is φ = 21331440.

The previous prime is 21400121. The next prime is 21400151. The reversal of 21400123 is 32100412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21400123 - 2¹ = 21400121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21400121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33873 + ... + 34498.

It is an arithmetic number, because the mean of its divisors is an integer number (5367202).

Almost surely, 2^21400123 is an apocalyptic number.

21400123 is a deficient number, since it is larger than the sum of its proper divisors (68685).

21400123 is an equidigital number, since it uses as much as digits as its factorization.

21400123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68684.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21400123 is about 4626.0266968534. The cubic root of 21400123 is about 277.6336417674.

Adding to 21400123 its reverse (32100412), we get a palindrome (53500535).

The spelling of 21400123 in words is "twenty-one million, four hundred thousand, one hundred twenty-three".