21764442 has 64 divisors (see below), whose sum is σ = 52254720. Its totient is φ = 5912256.

The previous prime is 21764441. The next prime is 21764447. The reversal of 21764442 is 24446712.

It is not an unprimeable number, because it can be changed into a prime (21764441) 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 31 ways as a sum of consecutive naturals, for example, 130243 + ... + 130409.

It is an arithmetic number, because the mean of its divisors is an integer number (816480).

Almost surely, 2^21764442 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21764442, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26127360).

21764442 is an abundant number, since it is smaller than the sum of its proper divisors (30490278).

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

21764442 is a wasteful number, since it uses less digits than its factorization.

21764442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 315.

The product of its digits is 10752, while the sum is 30.

The square root of 21764442 is about 4665.2376145273. The cubic root of 21764442 is about 279.2002775700.

The spelling of 21764442 in words is "twenty-one million, seven hundred sixty-four thousand, four hundred forty-two".