21684157533 has 6 divisors (see below), whose sum is σ = 31321560894. Its totient is φ = 14456105016.

The previous prime is 21684157513. The next prime is 21684157571. The reversal of 21684157533 is 33575148612.

It is a happy number.

21684157533 is a `hidden beast` number, since 2 + 1 + 6 + 8 + 41 + 575 + 33 = 666.

It can be written as a sum of positive squares in only one way, i.e., 15929721369 + 5754436164 = 126213^2 + 75858^2 .

It is not a de Polignac number, because 21684157533 - 2²² = 21679963229 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684157513) 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, 1204675410 + ... + 1204675427.

It is an arithmetic number, because the mean of its divisors is an integer number (5220260149).

Almost surely, 2^21684157533 is an apocalyptic number.

It is an amenable number.

21684157533 is a deficient number, since it is larger than the sum of its proper divisors (9637403361).

21684157533 is a wasteful number, since it uses less digits than its factorization.

21684157533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2409350843 (or 2409350840 counting only the distinct ones).

The product of its digits is 604800, while the sum is 45.

The spelling of 21684157533 in words is "twenty-one billion, six hundred eighty-four million, one hundred fifty-seven thousand, five hundred thirty-three".