21657236533 has 2 divisors, whose sum is σ = 21657236534. Its totient is φ = 21657236532.

The previous prime is 21657236483. The next prime is 21657236539. The reversal of 21657236533 is 33563275612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18310961124 + 3346275409 = 135318^2 + 57847^2 .

It is a cyclic number.

It is not a de Polignac number, because 21657236533 - 2⁹ = 21657236021 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21657236533.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21657236539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828618266 + 10828618267.

It is an arithmetic number, because the mean of its divisors is an integer number (10828618267).

Almost surely, 2^21657236533 is an apocalyptic number.

It is an amenable number.

21657236533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657236533 is an equidigital number, since it uses as much as digits as its factorization.

21657236533 is an evil number, because the sum of its binary digits is even.

The product of its digits is 680400, while the sum is 43.

The spelling of 21657236533 in words is "twenty-one billion, six hundred fifty-seven million, two hundred thirty-six thousand, five hundred thirty-three".