21172133 has 2 divisors, whose sum is σ = 21172134. Its totient is φ = 21172132.

The previous prime is 21172097. The next prime is 21172139. The reversal of 21172133 is 33127112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11142244 + 10029889 = 3338^2 + 3167^2 .

It is a cyclic number.

It is not a de Polignac number, because 21172133 - 2¹⁸ = 20909989 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21172139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10586066 + 10586067.

It is an arithmetic number, because the mean of its divisors is an integer number (10586067).

Almost surely, 2^21172133 is an apocalyptic number.

It is an amenable number.

21172133 is a deficient number, since it is larger than the sum of its proper divisors (1).

21172133 is an equidigital number, since it uses as much as digits as its factorization.

21172133 is an evil number, because the sum of its binary digits is even.

The product of its digits is 252, while the sum is 20.

The square root of 21172133 is about 4601.3186153536. The cubic root of 21172133 is about 276.6441798791.

Adding to 21172133 its reverse (33127112), we get a palindrome (54299245).

The spelling of 21172133 in words is "twenty-one million, one hundred seventy-two thousand, one hundred thirty-three".