21840404 has 6 divisors (see below), whose sum is σ = 38220714. Its totient is φ = 10920200.

The previous prime is 21840391. The next prime is 21840407. The reversal of 21840404 is 40404812.

It can be written as a sum of positive squares in only one way, i.e., 15984004 + 5856400 = 3998^2 + 2420^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21840404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21840407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2730047 + ... + 2730054.

It is an arithmetic number, because the mean of its divisors is an integer number (6370119).

Almost surely, 2^21840404 is an apocalyptic number.

It is an amenable number.

21840404 is a deficient number, since it is larger than the sum of its proper divisors (16380310).

21840404 is a wasteful number, since it uses less digits than its factorization.

21840404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5460105 (or 5460103 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 23.

The square root of 21840404 is about 4673.3718020290. The cubic root of 21840404 is about 279.5247209166.

The spelling of 21840404 in words is "twenty-one million, eight hundred forty thousand, four hundred four".