21851560 has 16 divisors (see below), whose sum is σ = 49166100. Its totient is φ = 8740608.

The previous prime is 21851549. The next prime is 21851561. The reversal of 21851560 is 6515812.

It can be written as a sum of positive squares in 2 ways, for example, as 21659716 + 191844 = 4654^2 + 438^2 .

It is not an unprimeable number, because it can be changed into a prime (21851561) 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 3 ways as a sum of consecutive naturals, for example, 273105 + ... + 273184.

Almost surely, 2^21851560 is an apocalyptic number.

21851560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21851560 is an abundant number, since it is smaller than the sum of its proper divisors (27314540).

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

21851560 is a wasteful number, since it uses less digits than its factorization.

21851560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546300 (or 546296 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 21851560 is about 4674.5652204242. The cubic root of 21851560 is about 279.5723062236.

The spelling of 21851560 in words is "twenty-one million, eight hundred fifty-one thousand, five hundred sixty".