21092971 has 4 divisors (see below), whose sum is σ = 22333752. Its totient is φ = 19852192.

The previous prime is 21092969. The next prime is 21092977. The reversal of 21092971 is 17929012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21092971 - 2¹ = 21092969 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21092977) 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 3 ways as a sum of consecutive naturals, for example, 620365 + ... + 620398.

It is an arithmetic number, because the mean of its divisors is an integer number (5583438).

Almost surely, 2^21092971 is an apocalyptic number.

21092971 is a deficient number, since it is larger than the sum of its proper divisors (1240781).

21092971 is a wasteful number, since it uses less digits than its factorization.

21092971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1240780.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 21092971 is about 4592.7084601573. The cubic root of 21092971 is about 276.2989610400.

The spelling of 21092971 in words is "twenty-one million, ninety-two thousand, nine hundred seventy-one".