21187071 has 24 divisors (see below), whose sum is σ = 33621120. Its totient is φ = 12797136.

The previous prime is 21187063. The next prime is 21187079. The reversal of 21187071 is 17078112.

It is an interprime number because it is at equal distance from previous prime (21187063) and next prime (21187079).

It is not a de Polignac number, because 21187071 - 2³ = 21187063 is a prime.

It is a congruent 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 23 ways as a sum of consecutive naturals, for example, 1240 + ... + 6626.

It is an arithmetic number, because the mean of its divisors is an integer number (1400880).

Almost surely, 2^21187071 is an apocalyptic number.

21187071 is a deficient number, since it is larger than the sum of its proper divisors (12434049).

21187071 is a wasteful number, since it uses less digits than its factorization.

21187071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5435 (or 5432 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 27.

The square root of 21187071 is about 4602.9415594813. The cubic root of 21187071 is about 276.7092266908.

The spelling of 21187071 in words is "twenty-one million, one hundred eighty-seven thousand, seventy-one".