21519894 has 48 divisors (see below), whose sum is σ = 49803840. Its totient is φ = 6130800.

The previous prime is 21519877. The next prime is 21519907. The reversal of 21519894 is 49891512.

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 23 ways as a sum of consecutive naturals, for example, 164209 + ... + 164339.

It is an arithmetic number, because the mean of its divisors is an integer number (1037580).

Almost surely, 2^21519894 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21519894, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24901920).

21519894 is an abundant number, since it is smaller than the sum of its proper divisors (28283946).

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

21519894 is a wasteful number, since it uses less digits than its factorization.

21519894 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297 (or 166 counting only the distinct ones).

The product of its digits is 25920, while the sum is 39.

The square root of 21519894 is about 4638.9539769220. The cubic root of 21519894 is about 278.1506265828.

It can be divided in two parts, 21 and 519894, that added together give a palindrome (519915).

The spelling of 21519894 in words is "twenty-one million, five hundred nineteen thousand, eight hundred ninety-four".