21172637 has 2 divisors, whose sum is σ = 21172638. Its totient is φ = 21172636.

The previous prime is 21172601. The next prime is 21172643. The reversal of 21172637 is 73627112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10797796 + 10374841 = 3286^2 + 3221^2 .

It is a cyclic number.

It is not a de Polignac number, because 21172637 - 2⁸ = 21172381 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 (21172037) 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 as a sum of consecutive naturals, namely, 10586318 + 10586319.

It is an arithmetic number, because the mean of its divisors is an integer number (10586319).

Almost surely, 2^21172637 is an apocalyptic number.

It is an amenable number.

21172637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21172637 is an equidigital number, since it uses as much as digits as its factorization.

21172637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3528, while the sum is 29.

The square root of 21172637 is about 4601.3733819372. The cubic root of 21172637 is about 276.6463750218.

Adding to 21172637 its reverse (73627112), we get a palindrome (94799749).

The spelling of 21172637 in words is "twenty-one million, one hundred seventy-two thousand, six hundred thirty-seven".