21090164 has 6 divisors (see below), whose sum is σ = 36907794. Its totient is φ = 10545080.

The previous prime is 21090161. The next prime is 21090197. The reversal of 21090164 is 46109012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 16337764 + 4752400 = 4042^2 + 2180^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2636267 + ... + 2636274.

It is an arithmetic number, because the mean of its divisors is an integer number (6151299).

Almost surely, 2^21090164 is an apocalyptic number.

It is an amenable number.

21090164 is a deficient number, since it is larger than the sum of its proper divisors (15817630).

21090164 is a wasteful number, since it uses less digits than its factorization.

21090164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5272545 (or 5272543 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21090164 is about 4592.4028568931. The cubic root of 21090164 is about 276.2867041039.

Adding to 21090164 its reverse (46109012), we get a palindrome (67199176).

The spelling of 21090164 in words is "twenty-one million, ninety thousand, one hundred sixty-four".