21242525 has 6 divisors (see below), whose sum is σ = 26340762. Its totient is φ = 16994000.

The previous prime is 21242521. The next prime is 21242527. The reversal of 21242525 is 52524212.

It can be written as a sum of positive squares in 3 ways, for example, as 784996 + 20457529 = 886^2 + 4523^2 .

It is not a de Polignac number, because 21242525 - 2² = 21242521 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21242525.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242521) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 424826 + ... + 424875.

It is an arithmetic number, because the mean of its divisors is an integer number (4390127).

Almost surely, 2^21242525 is an apocalyptic number.

21242525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21242525 is a deficient number, since it is larger than the sum of its proper divisors (5098237).

21242525 is an equidigital number, since it uses as much as digits as its factorization.

21242525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 849711 (or 849706 counting only the distinct ones).

The product of its digits is 1600, while the sum is 23.

The square root of 21242525 is about 4608.9613797471. The cubic root of 21242525 is about 276.9504314245.

Adding to 21242525 its reverse (52524212), we get a palindrome (73766737).

The spelling of 21242525 in words is "twenty-one million, two hundred forty-two thousand, five hundred twenty-five".