21526640 has 40 divisors (see below), whose sum is σ = 51277968. Its totient is φ = 8399360.

The previous prime is 21526633. The next prime is 21526649. The reversal of 21526640 is 4662512.

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

It is a plaindrome in base 3 and base 9.

It is a zygodrome in base 3 and base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21526649) 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, 2 + ... + 6561.

Almost surely, 2^21526640 is an apocalyptic number.

21526640 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 21526640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25638984).

21526640 is an abundant number, since it is smaller than the sum of its proper divisors (29751328).

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

21526640 is a wasteful number, since it uses less digits than its factorization.

21526640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6617 (or 6611 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21526640 is about 4639.6810235188. The cubic root of 21526640 is about 278.1796881896.

The spelling of 21526640 in words is "twenty-one million, five hundred twenty-six thousand, six hundred forty".