21045816 has 48 divisors (see below), whose sum is σ = 62183160. Its totient is φ = 6377280.

The previous prime is 21045811. The next prime is 21045853. The reversal of 21045816 is 61854012.

It is a super-2 number, since 2×21045816² = 885852742211712, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21045816.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21045811) 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, 12495 + ... + 14078.

Almost surely, 2^21045816 is an apocalyptic number.

It is an amenable number.

21045816 is an abundant number, since it is smaller than the sum of its proper divisors (41137344).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21045816 is a wasteful number, since it uses less digits than its factorization.

21045816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26596 (or 26589 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21045816 is about 4587.5719067934. The cubic root of 21045816 is about 276.0929113783.

Adding to 21045816 its reverse (61854012), we get a palindrome (82899828).

The spelling of 21045816 in words is "twenty-one million, forty-five thousand, eight hundred sixteen".