21100971 has 4 divisors (see below), whose sum is σ = 28134632. Its totient is φ = 14067312.

The previous prime is 21100969. The next prime is 21100993. The reversal of 21100971 is 17900112.

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

It is not a de Polignac number, because 21100971 - 2¹ = 21100969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21100901) 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, 3516826 + ... + 3516831.

It is an arithmetic number, because the mean of its divisors is an integer number (7033658).

Almost surely, 2^21100971 is an apocalyptic number.

21100971 is a deficient number, since it is larger than the sum of its proper divisors (7033661).

21100971 is an equidigital number, since it uses as much as digits as its factorization.

21100971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7033660.

The product of its (nonzero) digits is 126, while the sum is 21.

The square root of 21100971 is about 4593.5793233599. The cubic root of 21100971 is about 276.3338875612. Note that the first 3 decimals are identical.

The spelling of 21100971 in words is "twenty-one million, one hundred thousand, nine hundred seventy-one".