21455123 has 4 divisors (see below), whose sum is σ = 22584360. Its totient is φ = 20325888.

The previous prime is 21455117. The next prime is 21455143. The reversal of 21455123 is 32155412.

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 21455123 - 2⁴ = 21455107 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21455143) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 564590 + ... + 564627.

It is an arithmetic number, because the mean of its divisors is an integer number (5646090).

Almost surely, 2^21455123 is an apocalyptic number.

21455123 is a deficient number, since it is larger than the sum of its proper divisors (1129237).

21455123 is a wasteful number, since it uses less digits than its factorization.

21455123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1129236.

The product of its digits is 1200, while the sum is 23.

The square root of 21455123 is about 4631.9675085216. The cubic root of 21455123 is about 277.8712850646.

The spelling of 21455123 in words is "twenty-one million, four hundred fifty-five thousand, one hundred twenty-three".