21819924 has 36 divisors (see below), whose sum is σ = 63036064. Its totient is φ = 6234192.

The previous prime is 21819907. The next prime is 21819929. The reversal of 21819924 is 42991812.

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

It is a super-2 number, since 2×21819924² = 952218166731552, which contains 22 as substring.

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 (21819929) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 43042 + ... + 43545.

Almost surely, 2^21819924 is an apocalyptic number.

It is an amenable number.

21819924 is an abundant number, since it is smaller than the sum of its proper divisors (41216140).

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

21819924 is a wasteful number, since it uses less digits than its factorization.

21819924 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86604 (or 86599 counting only the distinct ones).

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

The square root of 21819924 is about 4671.1801506686. The cubic root of 21819924 is about 279.4373224024.

The spelling of 21819924 in words is "twenty-one million, eight hundred nineteen thousand, nine hundred twenty-four".