21856545 has 12 divisors (see below), whose sum is σ = 37884756. Its totient is φ = 11656800.

The previous prime is 21856537. The next prime is 21856579. The reversal of 21856545 is 54565812.

It can be written as a sum of positive squares in 2 ways, for example, as 4915089 + 16941456 = 2217^2 + 4116^2 .

It is not a de Polignac number, because 21856545 - 2³ = 21856537 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 242806 + ... + 242895.

It is an arithmetic number, because the mean of its divisors is an integer number (3157063).

Almost surely, 2^21856545 is an apocalyptic number.

It is an amenable number.

21856545 is a deficient number, since it is larger than the sum of its proper divisors (16028211).

21856545 is a wasteful number, since it uses less digits than its factorization.

21856545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 485712 (or 485709 counting only the distinct ones).

The product of its digits is 48000, while the sum is 36.

The square root of 21856545 is about 4675.0983946865. The cubic root of 21856545 is about 279.5935642326.

The spelling of 21856545 in words is "twenty-one million, eight hundred fifty-six thousand, five hundred forty-five".