21019440 has 80 divisors (see below), whose sum is σ = 70183008. Its totient is φ = 5173248.

The previous prime is 21019409. The next prime is 21019459. The reversal of 21019440 is 4491012.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 249 + ... + 6488.

Almost surely, 2^21019440 is an apocalyptic number.

21019440 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 21019440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35091504).

21019440 is an abundant number, since it is smaller than the sum of its proper divisors (49163568).

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

21019440 is a wasteful number, since it uses less digits than its factorization.

21019440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6766 (or 6760 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 21019440 is about 4584.6962821980. The cubic root of 21019440 is about 275.9775238996.

The spelling of 21019440 in words is "twenty-one million, nineteen thousand, four hundred forty".