21531253215 has 16 divisors (see below), whose sum is σ = 34604494848. Its totient is φ = 11431838496.

The previous prime is 21531253213. The next prime is 21531253223. The reversal of 21531253215 is 51235213512.

It is not a de Polignac number, because 21531253215 - 2¹ = 21531253213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531253213) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3215079 + ... + 3221768.

It is an arithmetic number, because the mean of its divisors is an integer number (2162780928).

Almost surely, 2^21531253215 is an apocalyptic number.

21531253215 is a deficient number, since it is larger than the sum of its proper divisors (13073241633).

21531253215 is a wasteful number, since it uses less digits than its factorization.

21531253215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6437078.

The product of its digits is 9000, while the sum is 30.

Adding to 21531253215 its reverse (51235213512), we get a palindrome (72766466727).

The spelling of 21531253215 in words is "twenty-one billion, five hundred thirty-one million, two hundred fifty-three thousand, two hundred fifteen".