21329640 has 96 divisors (see below), whose sum is σ = 69919200. Its totient is φ = 5639040.

The previous prime is 21329639. The next prime is 21329641. The reversal of 21329640 is 4692312.

21329640 is a `hidden beast` number, since 2 + 13 + 2 + 9 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (21329639) and next prime (21329641).

It is not an unprimeable number, because it can be changed into a prime (21329641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 64275 + ... + 64605.

It is an arithmetic number, because the mean of its divisors is an integer number (728325).

Almost surely, 2^21329640 is an apocalyptic number.

21329640 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 21329640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34959600).

21329640 is an abundant number, since it is smaller than the sum of its proper divisors (48589560).

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

21329640 is a wasteful number, since it uses less digits than its factorization.

21329640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 527 (or 520 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21329640 is about 4618.4023211496. The cubic root of 21329640 is about 277.3285037271.

The spelling of 21329640 in words is "twenty-one million, three hundred twenty-nine thousand, six hundred forty".