21519840 has 96 divisors (see below), whose sum is σ = 68584320. Its totient is φ = 5671424.

The previous prime is 21519821. The next prime is 21519847. The reversal of 21519840 is 4891512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21519798 and 21519807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21519847) 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 15 ways as a sum of consecutive naturals, for example, 51151 + ... + 51569.

It is an arithmetic number, because the mean of its divisors is an integer number (714420).

Almost surely, 2^21519840 is an apocalyptic number.

21519840 is a gapful number since it is divisible by the number (20) 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 21519840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34292160).

21519840 is an abundant number, since it is smaller than the sum of its proper divisors (47064480).

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

21519840 is a wasteful number, since it uses less digits than its factorization.

21519840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 544 (or 536 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 30.

The square root of 21519840 is about 4638.9481566407. The cubic root of 21519840 is about 278.1503939276.

The spelling of 21519840 in words is "twenty-one million, five hundred nineteen thousand, eight hundred forty".