21091271 has 8 divisors (see below), whose sum is σ = 22510080. Its totient is φ = 19692288.

The previous prime is 21091249. The next prime is 21091277. The reversal of 21091271 is 17219012.

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 21091271 - 2²² = 16896967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21091277) 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, 2726 + ... + 7043.

It is an arithmetic number, because the mean of its divisors is an integer number (2813760).

Almost surely, 2^21091271 is an apocalyptic number.

21091271 is a deficient number, since it is larger than the sum of its proper divisors (1418809).

21091271 is a wasteful number, since it uses less digits than its factorization.

21091271 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9913.

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 21091271 is about 4592.5233804522. The cubic root of 21091271 is about 276.2915380165.

The spelling of 21091271 in words is "twenty-one million, ninety-one thousand, two hundred seventy-one".