21399884 has 24 divisors (see below), whose sum is σ = 41160000. Its totient is φ = 9654480.

The previous prime is 21399839. The next prime is 21399901. The reversal of 21399884 is 48899312.

It is a happy number.

It is a Smith number, since the sum of its digits (44) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4367 + ... + 7865.

It is an arithmetic number, because the mean of its divisors is an integer number (1715000).

Almost surely, 2^21399884 is an apocalyptic number.

It is an amenable number.

21399884 is a deficient number, since it is larger than the sum of its proper divisors (19760116).

21399884 is a wasteful number, since it uses less digits than its factorization.

21399884 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3653 (or 3651 counting only the distinct ones).

The product of its digits is 124416, while the sum is 44.

The square root of 21399884 is about 4626.0008646778. Note that the first 3 decimals coincide. The cubic root of 21399884 is about 277.6326082113.

The spelling of 21399884 in words is "twenty-one million, three hundred ninety-nine thousand, eight hundred eighty-four".