21872140 has 24 divisors (see below), whose sum is σ = 46125072. Its totient is φ = 8712000.

The previous prime is 21872113. The next prime is 21872159. The reversal of 21872140 is 4127812.

It is a happy number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 2842 + ... + 7198.

It is an arithmetic number, because the mean of its divisors is an integer number (1921878).

Almost surely, 2^21872140 is an apocalyptic number.

21872140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21872140 is an abundant number, since it is smaller than the sum of its proper divisors (24252932).

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

21872140 is a wasteful number, since it uses less digits than its factorization.

21872140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4617 (or 4615 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21872140 is about 4676.7659766125. The cubic root of 21872140 is about 279.6600466068.

Adding to 21872140 its reverse (4127812), we get a palindrome (25999952).

The spelling of 21872140 in words is "twenty-one million, eight hundred seventy-two thousand, one hundred forty".