21016971 has 6 divisors (see below), whose sum is σ = 30357860. Its totient is φ = 14011308.

The previous prime is 21016949. The next prime is 21016979. The reversal of 21016971 is 17961012.

It is not a de Polignac number, because 21016971 - 2⁹ = 21016459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21016979) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1167601 + ... + 1167618.

Almost surely, 2^21016971 is an apocalyptic number.

21016971 is a deficient number, since it is larger than the sum of its proper divisors (9340889).

21016971 is a wasteful number, since it uses less digits than its factorization.

21016971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2335225 (or 2335222 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 21016971 is about 4584.4270089074. The cubic root of 21016971 is about 275.9667177889.

Adding to 21016971 its reverse (17961012), we get a palindrome (38977983).

The spelling of 21016971 in words is "twenty-one million, sixteen thousand, nine hundred seventy-one".