21291984 has 100 divisors (see below), whose sum is σ = 70458784. Its totient is φ = 6080832.

The previous prime is 21291971. The next prime is 21292013. The reversal of 21291984 is 48919212.

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

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 19 ways as a sum of consecutive naturals, for example, 7899 + ... + 10245.

Almost surely, 2^21291984 is an apocalyptic number.

21291984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21291984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35229392).

21291984 is an abundant number, since it is smaller than the sum of its proper divisors (49166800).

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

21291984 is a wasteful number, since it uses less digits than its factorization.

21291984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2374 (or 2359 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The square root of 21291984 is about 4614.3237857784. The cubic root of 21291984 is about 277.1652061799.

The spelling of 21291984 in words is "twenty-one million, two hundred ninety-one thousand, nine hundred eighty-four".