21509052 has 24 divisors (see below), whose sum is σ = 50265600. Its totient is φ = 7158576.

The previous prime is 21509041. The next prime is 21509057. The reversal of 21509052 is 25090512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21509057) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11349 + ... + 13107.

It is an arithmetic number, because the mean of its divisors is an integer number (2094400).

Almost surely, 2^21509052 is an apocalyptic number.

It is an amenable number.

21509052 is an abundant number, since it is smaller than the sum of its proper divisors (28756548).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21509052 is a wasteful number, since it uses less digits than its factorization.

21509052 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2785 (or 2783 counting only the distinct ones).

The product of its (nonzero) digits is 900, while the sum is 24.

The square root of 21509052 is about 4637.7852472921. The cubic root of 21509052 is about 278.1039067789.

Adding to 21509052 its reverse (25090512), we get a palindrome (46599564).

The spelling of 21509052 in words is "twenty-one million, five hundred nine thousand, fifty-two".