21381340 has 24 divisors (see below), whose sum is σ = 45017280. Its totient is φ = 8530368.

The previous prime is 21381317. The next prime is 21381361. The reversal of 21381340 is 4318312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8106 + ... + 10414.

It is an arithmetic number, because the mean of its divisors is an integer number (1875720).

Almost surely, 2^21381340 is an apocalyptic number.

21381340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21381340 is an abundant number, since it is smaller than the sum of its proper divisors (23635940).

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

21381340 is a wasteful number, since it uses less digits than its factorization.

21381340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2781 (or 2779 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21381340 is about 4623.9961072648. The cubic root of 21381340 is about 277.5523911578.

Adding to 21381340 its reverse (4318312), we get a palindrome (25699652).

The spelling of 21381340 in words is "twenty-one million, three hundred eighty-one thousand, three hundred forty".