21387760 has 40 divisors (see below), whose sum is σ = 50237856. Its totient is φ = 8467200.

The previous prime is 21387757. The next prime is 21387763. The reversal of 21387760 is 6778312.

It is an interprime number because it is at equal distance from previous prime (21387757) and next prime (21387763).

It is a tau number, because it is divible by the number of its divisors (40).

It is a Smith number, since the sum of its digits (34) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387763) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6757 + ... + 9403.

Almost surely, 2^21387760 is an apocalyptic number.

21387760 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 21387760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25118928).

21387760 is an abundant number, since it is smaller than the sum of its proper divisors (28850096).

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

21387760 is a wasteful number, since it uses less digits than its factorization.

21387760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2761 (or 2755 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 21387760 is about 4624.6902598985. The cubic root of 21387760 is about 277.5801678396.

The spelling of 21387760 in words is "twenty-one million, three hundred eighty-seven thousand, seven hundred sixty".