21373440 has 240 divisors, whose sum is σ = 78369984. Its totient is φ = 4956160.

The previous prime is 21373411. The next prime is 21373447. The reversal of 21373440 is 4437312.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21373440.

It is not an unprimeable number, because it can be changed into a prime (21373447) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 929269 + ... + 929291.

Almost surely, 2^21373440 is an apocalyptic number.

21373440 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 21373440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39184992).

21373440 is an abundant number, since it is smaller than the sum of its proper divisors (56996544).

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

21373440 is a wasteful number, since it uses less digits than its factorization.

21373440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71 (or 44 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 24.

The square root of 21373440 is about 4623.1417888704. The cubic root of 21373440 is about 277.5182034970.

The spelling of 21373440 in words is "twenty-one million, three hundred seventy-three thousand, four hundred forty".