21681140 has 24 divisors (see below), whose sum is σ = 49033320. Its totient is φ = 8005248.

The previous prime is 21681113. The next prime is 21681151. The reversal of 21681140 is 4118612.

It can be written as a sum of positive squares in 4 ways, for example, as 355216 + 21325924 = 596^2 + 4618^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41435 + ... + 41954.

It is an arithmetic number, because the mean of its divisors is an integer number (2043055).

Almost surely, 2^21681140 is an apocalyptic number.

21681140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21681140 is an abundant number, since it is smaller than the sum of its proper divisors (27352180).

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

21681140 is a wasteful number, since it uses less digits than its factorization.

21681140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83411 (or 83409 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 21681140 is about 4656.3011071021. The cubic root of 21681140 is about 278.8436151213.

Adding to 21681140 its reverse (4118612), we get a palindrome (25799752).

The spelling of 21681140 in words is "twenty-one million, six hundred eighty-one thousand, one hundred forty".