21143440 has 40 divisors (see below), whose sum is σ = 51300288. Its totient is φ = 8088960.

The previous prime is 21143411. The next prime is 21143453. The reversal of 21143440 is 4434112.

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

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, 3906 + ... + 7585.

Almost surely, 2^21143440 is an apocalyptic number.

21143440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21143440 is an abundant number, since it is smaller than the sum of its proper divisors (30156848).

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

21143440 is a wasteful number, since it uses less digits than its factorization.

21143440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11527 (or 11521 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 21143440 is about 4598.1996476882. The cubic root of 21143440 is about 276.5191516960.

Adding to 21143440 its reverse (4434112), we get a palindrome (25577552).

The spelling of 21143440 in words is "twenty-one million, one hundred forty-three thousand, four hundred forty".