21640071240 has 128 divisors (see below), whose sum is σ = 72168336000. Its totient is φ = 5767905024.

The previous prime is 21640071227. The next prime is 21640071247. The reversal of 21640071240 is 4217004612.

21640071240 is a `hidden beast` number, since 2 + 1 + 640 + 0 + 7 + 12 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21640071247) 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 31 ways as a sum of consecutive naturals, for example, 3257202 + ... + 3263838.

It is an arithmetic number, because the mean of its divisors is an integer number (563815125).

Almost surely, 2^21640071240 is an apocalyptic number.

21640071240 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 21640071240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36084168000).

21640071240 is an abundant number, since it is smaller than the sum of its proper divisors (50528264760).

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

21640071240 is a wasteful number, since it uses less digits than its factorization.

21640071240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9676 (or 9666 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

Adding to 21640071240 its reverse (4217004612), we get a palindrome (25857075852).

The spelling of 21640071240 in words is "twenty-one billion, six hundred forty million, seventy-one thousand, two hundred forty".