21052551 has 16 divisors (see below), whose sum is σ = 31821440. Its totient is φ = 12273120.

The previous prime is 21052547. The next prime is 21052553. The reversal of 21052551 is 15525012.

It is not a de Polignac number, because 21052551 - 2² = 21052547 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21052553) 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 in 15 ways as a sum of consecutive naturals, for example, 13465 + ... + 14946.

It is an arithmetic number, because the mean of its divisors is an integer number (1988840).

Almost surely, 2^21052551 is an apocalyptic number.

21052551 is a deficient number, since it is larger than the sum of its proper divisors (10768889).

21052551 is a wasteful number, since it uses less digits than its factorization.

21052551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28446.

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 21052551 is about 4588.3058965156. The cubic root of 21052551 is about 276.1223596297.

Adding to 21052551 its reverse (15525012), we get a palindrome (36577563).

It can be divided in two parts, 2105 and 2551, that added together give a triangular number (4656 = T₉₆).

The spelling of 21052551 in words is "twenty-one million, fifty-two thousand, five hundred fifty-one".