21533153521 has 4 divisors (see below), whose sum is σ = 23490712944. Its totient is φ = 19575594100.

The previous prime is 21533153491. The next prime is 21533153531. The reversal of 21533153521 is 12535133512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21533153521 - 2²¹ = 21531056369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21533153531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 978779695 + ... + 978779716.

It is an arithmetic number, because the mean of its divisors is an integer number (5872678236).

Almost surely, 2^21533153521 is an apocalyptic number.

It is an amenable number.

21533153521 is a deficient number, since it is larger than the sum of its proper divisors (1957559423).

21533153521 is a wasteful number, since it uses less digits than its factorization.

21533153521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1957559422.

The product of its digits is 13500, while the sum is 31.

The spelling of 21533153521 in words is "twenty-one billion, five hundred thirty-three million, one hundred fifty-three thousand, five hundred twenty-one".