21275971 has 4 divisors (see below), whose sum is σ = 21532392. Its totient is φ = 21019552.

The previous prime is 21275941. The next prime is 21275981. The reversal of 21275971 is 17957212.

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

It is a cyclic number.

It is not a de Polignac number, because 21275971 - 2¹⁹ = 20751683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21275941) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 128086 + ... + 128251.

It is an arithmetic number, because the mean of its divisors is an integer number (5383098).

Almost surely, 2^21275971 is an apocalyptic number.

21275971 is a deficient number, since it is larger than the sum of its proper divisors (256421).

21275971 is an equidigital number, since it uses as much as digits as its factorization.

21275971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256420.

The product of its digits is 8820, while the sum is 34.

The square root of 21275971 is about 4612.5883189376. The cubic root of 21275971 is about 277.0957064795.

The spelling of 21275971 in words is "twenty-one million, two hundred seventy-five thousand, nine hundred seventy-one".