21236432565 has 48 divisors (see below), whose sum is σ = 36122667840. Its totient is φ = 10649802240.

The previous prime is 21236432491. The next prime is 21236432587. The reversal of 21236432565 is 56523463212.

It is not a de Polignac number, because 21236432565 - 2¹² = 21236428469 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 445485 + ... + 490845.

It is an arithmetic number, because the mean of its divisors is an integer number (752555580).

Almost surely, 2^21236432565 is an apocalyptic number.

It is an amenable number.

21236432565 is a deficient number, since it is larger than the sum of its proper divisors (14886235275).

21236432565 is a wasteful number, since it uses less digits than its factorization.

21236432565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45474 (or 45451 counting only the distinct ones).

The product of its digits is 259200, while the sum is 39.

Adding to 21236432565 its reverse (56523463212), we get a palindrome (77759895777).

The spelling of 21236432565 in words is "twenty-one billion, two hundred thirty-six million, four hundred thirty-two thousand, five hundred sixty-five".