21144764 has 6 divisors (see below), whose sum is σ = 37003344. Its totient is φ = 10572380.

The previous prime is 21144763. The next prime is 21144769. The reversal of 21144764 is 46744112.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21144763) 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, 2643092 + ... + 2643099.

It is an arithmetic number, because the mean of its divisors is an integer number (6167224).

Almost surely, 2^21144764 is an apocalyptic number.

It is an amenable number.

21144764 is a deficient number, since it is larger than the sum of its proper divisors (15858580).

21144764 is a wasteful number, since it uses less digits than its factorization.

21144764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5286195 (or 5286193 counting only the distinct ones).

The product of its digits is 5376, while the sum is 29.

The square root of 21144764 is about 4598.3436148248. The cubic root of 21144764 is about 276.5249234423.

Adding to 21144764 its reverse (46744112), we get a palindrome (67888876).

The spelling of 21144764 in words is "twenty-one million, one hundred forty-four thousand, seven hundred sixty-four".