21001984 has 18 divisors (see below), whose sum is σ = 41922440. Its totient is φ = 10500864.

The previous prime is 21001979. The next prime is 21001991. The reversal of 21001984 is 48910012.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40764 + ... + 41275.

Almost surely, 2^21001984 is an apocalyptic number.

It is an amenable number.

21001984 is a deficient number, since it is larger than the sum of its proper divisors (20920456).

21001984 is an frugal number, since it uses more digits than its factorization.

21001984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82055 (or 82041 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21001984 is about 4582.7921619903. The cubic root of 21001984 is about 275.9011057860.

Adding to 21001984 its reverse (48910012), we get a palindrome (69911996).

The spelling of 21001984 in words is "twenty-one million, one thousand, nine hundred eighty-four".