21172011 has 16 divisors (see below), whose sum is σ = 32408064. Its totient is φ = 12043584.

The previous prime is 21172009. The next prime is 21172037. The reversal of 21172011 is 11027112.

It is not a de Polignac number, because 21172011 - 2¹ = 21172009 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21174011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2730 + ... + 7056.

It is an arithmetic number, because the mean of its divisors is an integer number (2025504).

Almost surely, 2^21172011 is an apocalyptic number.

21172011 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21172011 is a deficient number, since it is larger than the sum of its proper divisors (11236053).

21172011 is a wasteful number, since it uses less digits than its factorization.

21172011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4570.

The product of its (nonzero) digits is 28, while the sum is 15.

The square root of 21172011 is about 4601.3053582652. The cubic root of 21172011 is about 276.6436485100.

Adding to 21172011 its reverse (11027112), we get a palindrome (32199123).

The spelling of 21172011 in words is "twenty-one million, one hundred seventy-two thousand, eleven".