21052756 has 6 divisors (see below), whose sum is σ = 36842330. Its totient is φ = 10526376.

The previous prime is 21052739. The next prime is 21052769. The reversal of 21052756 is 65725012.

It can be written as a sum of positive squares in only one way, i.e., 19660356 + 1392400 = 4434^2 + 1180^2 .

It is a congruent number.

It is an unprimeable number.

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, 2631591 + ... + 2631598.

Almost surely, 2^21052756 is an apocalyptic number.

It is an amenable number.

21052756 is a deficient number, since it is larger than the sum of its proper divisors (15789574).

21052756 is a wasteful number, since it uses less digits than its factorization.

21052756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5263193 (or 5263191 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 21052756 is about 4588.3282358611. The cubic root of 21052756 is about 276.1232558774.

Adding to 21052756 its reverse (65725012), we get a palindrome (86777768).

The spelling of 21052756 in words is "twenty-one million, fifty-two thousand, seven hundred fifty-six".