21091017 has 16 divisors (see below), whose sum is σ = 28588032. Its totient is φ = 13829760.

The previous prime is 21091009. The next prime is 21091051. The reversal of 21091017 is 71019012.

It is not a de Polignac number, because 21091017 - 2³ = 21091009 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21090984 and 21091002.

It is not an unprimeable number, because it can be changed into a prime (21091717) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74917 + ... + 75197.

It is an arithmetic number, because the mean of its divisors is an integer number (1786752).

Almost surely, 2^21091017 is an apocalyptic number.

It is an amenable number.

21091017 is a deficient number, since it is larger than the sum of its proper divisors (7497015).

21091017 is a wasteful number, since it uses less digits than its factorization.

21091017 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 608.

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

The square root of 21091017 is about 4592.4957267264. The cubic root of 21091017 is about 276.2904288953.

The spelling of 21091017 in words is "twenty-one million, ninety-one thousand, seventeen".