21187073 has 8 divisors (see below), whose sum is σ = 21646440. Its totient is φ = 20732800.

The previous prime is 21187063. The next prime is 21187079. The reversal of 21187073 is 37078112.

It can be written as a sum of positive squares in 4 ways, for example, as 2455489 + 18731584 = 1567^2 + 4328^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21187073 - 2⁸ = 21186817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21187079) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7811 + ... + 10167.

It is an arithmetic number, because the mean of its divisors is an integer number (2705805).

Almost surely, 2^21187073 is an apocalyptic number.

It is an amenable number.

21187073 is a deficient number, since it is larger than the sum of its proper divisors (459367).

21187073 is a wasteful number, since it uses less digits than its factorization.

21187073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2547.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 21187073 is about 4602.9417767337. The cubic root of 21187073 is about 276.7092353976.

The spelling of 21187073 in words is "twenty-one million, one hundred eighty-seven thousand, seventy-three".