21861140 has 24 divisors (see below), whose sum is σ = 52467072. Its totient is φ = 7495200.

The previous prime is 21861139. The next prime is 21861143. The reversal of 21861140 is 4116812.

21861140 = T₈₉ + T₉₀ + ... + T₅₀₈.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21861143) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77936 + ... + 78215.

It is an arithmetic number, because the mean of its divisors is an integer number (2186128).

Almost surely, 2^21861140 is an apocalyptic number.

21861140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21861140 is an abundant number, since it is smaller than the sum of its proper divisors (30605932).

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

21861140 is a wasteful number, since it uses less digits than its factorization.

21861140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156167 (or 156165 counting only the distinct ones).

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

The square root of 21861140 is about 4675.5898023672. The cubic root of 21861140 is about 279.6131562649.

Adding to 21861140 its reverse (4116812), we get a palindrome (25977952).

The spelling of 21861140 in words is "twenty-one million, eight hundred sixty-one thousand, one hundred forty".