21143988 has 36 divisors (see below), whose sum is σ = 56592900. Its totient is φ = 6633216.

The previous prime is 21143981. The next prime is 21143999. The reversal of 21143988 is 88934112.

21143988 is a `hidden beast` number, since 211 + 439 + 8 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 18766224 + 2377764 = 4332^2 + 1542^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21143981) 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, 16663 + ... + 17886.

It is an arithmetic number, because the mean of its divisors is an integer number (1572025).

Almost surely, 2^21143988 is an apocalyptic number.

It is an amenable number.

21143988 is an abundant number, since it is smaller than the sum of its proper divisors (35448912).

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

21143988 is a wasteful number, since it uses less digits than its factorization.

21143988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34576 (or 34571 counting only the distinct ones).

The product of its digits is 13824, while the sum is 36.

The square root of 21143988 is about 4598.2592358413. The cubic root of 21143988 is about 276.5215406353.

The spelling of 21143988 in words is "twenty-one million, one hundred forty-three thousand, nine hundred eighty-eight".