21011984 has 30 divisors (see below), whose sum is σ = 47359134. Its totient is φ = 9004800.

The previous prime is 21011981. The next prime is 21012053. The reversal of 21011984 is 48911012.

It can be written as a sum of positive squares in only one way, i.e., 16483600 + 4528384 = 4060^2 + 2128^2 .

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21011981) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12617 + ... + 14184.

Almost surely, 2^21011984 is an apocalyptic number.

It is an amenable number.

21011984 is an abundant number, since it is smaller than the sum of its proper divisors (26347150).

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

21011984 is a wasteful number, since it uses less digits than its factorization.

21011984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26823 (or 26810 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 21011984 is about 4583.8830700619. The cubic root of 21011984 is about 275.9448885270.

Adding to 21011984 its reverse (48911012), we get a palindrome (69922996).

The spelling of 21011984 in words is "twenty-one million, eleven thousand, nine hundred eighty-four".