21486645 has 18 divisors (see below), whose sum is σ = 37297494. Its totient is φ = 11442960.

The previous prime is 21486637. The next prime is 21486649. The reversal of 21486645 is 54668412.

21486645 is a `hidden beast` number, since 2 + 1 + 4 + 8 + 6 + 645 = 666.

It can be written as a sum of positive squares in only one way, i.e., 17189316 + 4297329 = 4146^2 + 2073^2 .

It is not a de Polignac number, because 21486645 - 2³ = 21486637 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21486649) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 30750 + ... + 31440.

It is an arithmetic number, because the mean of its divisors is an integer number (2072083).

Almost surely, 2^21486645 is an apocalyptic number.

It is an amenable number.

21486645 is a deficient number, since it is larger than the sum of its proper divisors (15810849).

21486645 is an frugal number, since it uses more digits than its factorization.

21486645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1393 (or 699 counting only the distinct ones).

The product of its digits is 46080, while the sum is 36.

The square root of 21486645 is about 4635.3689173571. The cubic root of 21486645 is about 278.0073018802.

Multiplying 21486645 by its product of digits (46080), we get a square (990104601600 = 995040²).

The spelling of 21486645 in words is "twenty-one million, four hundred eighty-six thousand, six hundred forty-five".