21875805 has 48 divisors (see below), whose sum is σ = 45253440. Its totient is φ = 9997344.

The previous prime is 21875797. The next prime is 21875827. The reversal of 21875805 is 50857812.

21875805 is a nontrivial binomial coefficient, being equal to C(6615, 2).

It is not a de Polignac number, because 21875805 - 2³ = 21875797 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21875805.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4962 + ... + 8268.

It is an arithmetic number, because the mean of its divisors is an integer number (942780).

Almost surely, 2^21875805 is an apocalyptic number.

21875805 is the 6614-th triangular number.

It is an amenable number.

21875805 is an abundant number, since it is smaller than the sum of its proper divisors (23377635).

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

21875805 is a wasteful number, since it uses less digits than its factorization.

21875805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3335 (or 3322 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The square root of 21875805 is about 4677.1577907956. The cubic root of 21875805 is about 279.6756661244.

It can be divided in two parts, 21 and 875805, that added together give a triangular number (875826 = T₁₃₂₃).

The spelling of 21875805 in words is "twenty-one million, eight hundred seventy-five thousand, eight hundred five".