21545878 has 16 divisors (see below), whose sum is σ = 33140016. Its totient is φ = 10501920.

The previous prime is 21545863. The next prime is 21545879. The reversal of 21545878 is 87854512.

It is a self number, because there is not a number n which added to its sum of digits gives 21545878.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545879) 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 7 ways as a sum of consecutive naturals, for example, 18625 + ... + 19747.

It is an arithmetic number, because the mean of its divisors is an integer number (2071251).

Almost surely, 2^21545878 is an apocalyptic number.

21545878 is a deficient number, since it is larger than the sum of its proper divisors (11594138).

21545878 is a wasteful number, since it uses less digits than its factorization.

21545878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1359.

The product of its digits is 89600, while the sum is 40.

The square root of 21545878 is about 4641.7537633959. The cubic root of 21545878 is about 278.2625317022.

The spelling of 21545878 in words is "twenty-one million, five hundred forty-five thousand, eight hundred seventy-eight".