21123045 has 16 divisors (see below), whose sum is σ = 37552320. Its totient is φ = 11265552.

The previous prime is 21123043. The next prime is 21123073. The reversal of 21123045 is 54032112.

It is not a de Polignac number, because 21123045 - 2¹ = 21123043 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78099 + ... + 78368.

It is an arithmetic number, because the mean of its divisors is an integer number (2347020).

Almost surely, 2^21123045 is an apocalyptic number.

It is an amenable number.

21123045 is a deficient number, since it is larger than the sum of its proper divisors (16429275).

21123045 is a wasteful number, since it uses less digits than its factorization.

21123045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156481 (or 156475 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21123045 is about 4595.9813968292. The cubic root of 21123045 is about 276.4302128037.

Adding to 21123045 its reverse (54032112), we get a palindrome (75155157).

The spelling of 21123045 in words is "twenty-one million, one hundred twenty-three thousand, forty-five".