21821144 has 16 divisors (see below), whose sum is σ = 40979400. Its totient is φ = 10893312.

The previous prime is 21821141. The next prime is 21821147. The reversal of 21821144 is 44112812.

It is an interprime number because it is at equal distance from previous prime (21821141) and next prime (21821147).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4379 + ... + 7925.

Almost surely, 2^21821144 is an apocalyptic number.

It is an amenable number.

21821144 is a deficient number, since it is larger than the sum of its proper divisors (19158256).

21821144 is a wasteful number, since it uses less digits than its factorization.

21821144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4322 (or 4318 counting only the distinct ones).

The product of its digits is 512, while the sum is 23.

The square root of 21821144 is about 4671.3107368275. The cubic root of 21821144 is about 279.4425302907.

Adding to 21821144 its reverse (44112812), we get a palindrome (65933956).

The spelling of 21821144 in words is "twenty-one million, eight hundred twenty-one thousand, one hundred forty-four".