21000045 has 32 divisors (see below), whose sum is σ = 36961920. Its totient is φ = 10096640.

The previous prime is 21000041. The next prime is 21000059. The reversal of 21000045 is 54000012.

It is not a de Polignac number, because 21000045 - 2² = 21000041 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000041) 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 31 ways as a sum of consecutive naturals, for example, 22141 + ... + 23069.

It is an arithmetic number, because the mean of its divisors is an integer number (1155060).

Almost surely, 2^21000045 is an apocalyptic number.

It is an amenable number.

21000045 is a deficient number, since it is larger than the sum of its proper divisors (15961875).

21000045 is a wasteful number, since it uses less digits than its factorization.

21000045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1085.

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 21000045 is about 4582.5806048557. The cubic root of 21000045 is about 275.8926147040.

Adding to 21000045 its reverse (54000012), we get a palindrome (75000057).

The spelling of 21000045 in words is "twenty-one million, forty-five", and thus it is an aban number and an uban number.