21017091 has 4 divisors (see below), whose sum is σ = 28022792. Its totient is φ = 14011392.

The previous prime is 21017071. The next prime is 21017093. The reversal of 21017091 is 19071012.

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

It is not a de Polignac number, because 21017091 - 2⁶ = 21017027 is a prime.

It is a super-2 number, since 2×21017091² = 883436228204562, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21017093) 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, 3502846 + ... + 3502851.

It is an arithmetic number, because the mean of its divisors is an integer number (7005698).

Almost surely, 2^21017091 is an apocalyptic number.

21017091 is a deficient number, since it is larger than the sum of its proper divisors (7005701).

21017091 is an equidigital number, since it uses as much as digits as its factorization.

21017091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7005700.

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

The square root of 21017091 is about 4584.4400966748. The cubic root of 21017091 is about 275.9672430143.

The spelling of 21017091 in words is "twenty-one million, seventeen thousand, ninety-one".