21533251225 has 12 divisors (see below), whose sum is σ = 26792371116. Its totient is φ = 17167801280.

The previous prime is 21533251219. The next prime is 21533251253. The reversal of 21533251225 is 52215233512.

It can be written as a sum of positive squares in 6 ways, for example, as 220463104 + 21312788121 = 14848^2 + 145989^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21533251225 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1462522 + ... + 1477171.

It is an arithmetic number, because the mean of its divisors is an integer number (2232697593).

Almost surely, 2^21533251225 is an apocalyptic number.

21533251225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21533251225 is a deficient number, since it is larger than the sum of its proper divisors (5259119891).

21533251225 is a wasteful number, since it uses less digits than its factorization.

21533251225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2939996 (or 2939991 counting only the distinct ones).

The product of its digits is 18000, while the sum is 31.

Adding to 21533251225 its reverse (52215233512), we get a palindrome (73748484737).

The spelling of 21533251225 in words is "twenty-one billion, five hundred thirty-three million, two hundred fifty-one thousand, two hundred twenty-five".