21035640 has 64 divisors (see below), whose sum is σ = 63423360. Its totient is φ = 5581440.

The previous prime is 21035633. The next prime is 21035687. The reversal of 21035640 is 4653012.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36555 + ... + 37125.

It is an arithmetic number, because the mean of its divisors is an integer number (990990).

Almost surely, 2^21035640 is an apocalyptic number.

21035640 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 21035640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31711680).

21035640 is an abundant number, since it is smaller than the sum of its proper divisors (42387720).

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

21035640 is a wasteful number, since it uses less digits than its factorization.

21035640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 892 (or 888 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21035640 is about 4586.4626892628. The cubic root of 21035640 is about 276.0484057087.

Adding to 21035640 its reverse (4653012), we get a palindrome (25688652).

The spelling of 21035640 in words is "twenty-one million, thirty-five thousand, six hundred forty".