21166645 has 8 divisors (see below), whose sum is σ = 26219520. Its totient is φ = 16386960.

The previous prime is 21166643. The next prime is 21166679. The reversal of 21166645 is 54666112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21166645 - 2¹ = 21166643 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166643) 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 7 ways as a sum of consecutive naturals, for example, 68125 + ... + 68434.

It is an arithmetic number, because the mean of its divisors is an integer number (3277440).

Almost surely, 2^21166645 is an apocalyptic number.

It is an amenable number.

21166645 is a deficient number, since it is larger than the sum of its proper divisors (5052875).

21166645 is a wasteful number, since it uses less digits than its factorization.

21166645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136595.

The product of its digits is 8640, while the sum is 31.

The square root of 21166645 is about 4600.7222259119. The cubic root of 21166645 is about 276.6202749588.

The spelling of 21166645 in words is "twenty-one million, one hundred sixty-six thousand, six hundred forty-five".