21693645 has 24 divisors (see below), whose sum is σ = 38817792. Its totient is φ = 11196000.

The previous prime is 21693641. The next prime is 21693667. The reversal of 21693645 is 54639612.

It is a happy number.

21693645 is a `hidden beast` number, since 2 + 1 + 6 + 9 + 3 + 645 = 666.

It is not a de Polignac number, because 21693645 - 2² = 21693641 is a prime.

It is a super-3 number, since 3×21693645³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21693641) 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 23 ways as a sum of consecutive naturals, for example, 6381 + ... + 9170.

It is an arithmetic number, because the mean of its divisors is an integer number (1617408).

Almost surely, 2^21693645 is an apocalyptic number.

It is an amenable number.

21693645 is a deficient number, since it is larger than the sum of its proper divisors (17124147).

21693645 is a wasteful number, since it uses less digits than its factorization.

21693645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15593 (or 15590 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 21693645 is about 4657.6437175894. The cubic root of 21693645 is about 278.8972142284.

The spelling of 21693645 in words is "twenty-one million, six hundred ninety-three thousand, six hundred forty-five".