21545018 has 24 divisors (see below), whose sum is σ = 37619316. Its totient is φ = 9215360.

The previous prime is 21545011. The next prime is 21545039. The reversal of 21545018 is 81054512.

It can be written as a sum of positive squares in 2 ways, for example, as 19070689 + 2474329 = 4367^2 + 1573^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21545011) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1496 + ... + 6732.

Almost surely, 2^21545018 is an apocalyptic number.

21545018 is a deficient number, since it is larger than the sum of its proper divisors (16074298).

21545018 is a wasteful number, since it uses less digits than its factorization.

21545018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5278 (or 5267 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 26.

The square root of 21545018 is about 4641.6611250715. The cubic root of 21545018 is about 278.2588293859.

The spelling of 21545018 in words is "twenty-one million, five hundred forty-five thousand, eighteen".