21505550636 has 6 divisors (see below), whose sum is σ = 37634713620. Its totient is φ = 10752775316.

The previous prime is 21505550621. The next prime is 21505550669. The reversal of 21505550636 is 63605550512.

It is a self number, because there is not a number n which added to its sum of digits gives 21505550636.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2688193826 + ... + 2688193833.

It is an arithmetic number, because the mean of its divisors is an integer number (6272452270).

Almost surely, 2^21505550636 is an apocalyptic number.

It is an amenable number.

21505550636 is a deficient number, since it is larger than the sum of its proper divisors (16129162984).

21505550636 is a wasteful number, since it uses less digits than its factorization.

21505550636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5376387663 (or 5376387661 counting only the distinct ones).

The product of its (nonzero) digits is 135000, while the sum is 38.

The spelling of 21505550636 in words is "twenty-one billion, five hundred five million, five hundred fifty thousand, six hundred thirty-six".