21375640 has 128 divisors (see below), whose sum is σ = 58605120. Its totient is φ = 6912000.

The previous prime is 21375631. The next prime is 21375659. The reversal of 21375640 is 4657312.

It is a junction number, because it is equal to n+sod(n) for n = 21375599 and 21375608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 211590 + ... + 211690.

Almost surely, 2^21375640 is an apocalyptic number.

21375640 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 21375640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29302560).

21375640 is an abundant number, since it is smaller than the sum of its proper divisors (37229480).

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

21375640 is a wasteful number, since it uses less digits than its factorization.

21375640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173 (or 169 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 28.

The square root of 21375640 is about 4623.3797161817. The cubic root of 21375640 is about 277.5277249576.

It can be divided in two parts, 2137 and 5640, that added together give a palindrome (7777).

The spelling of 21375640 in words is "twenty-one million, three hundred seventy-five thousand, six hundred forty".