21643012136 has 8 divisors (see below), whose sum is σ = 40580647770. Its totient is φ = 10821506064.

The previous prime is 21643012133. The next prime is 21643012159. The reversal of 21643012136 is 63121034612.

It can be written as a sum of positive squares in only one way, i.e., 21460492036 + 182520100 = 146494^2 + 13510^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 21643012099 and 21643012108.

It is not an unprimeable number, because it can be changed into a prime (21643012133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1352688251 + ... + 1352688266.

Almost surely, 2^21643012136 is an apocalyptic number.

It is an amenable number.

21643012136 is a deficient number, since it is larger than the sum of its proper divisors (18937635634).

21643012136 is a wasteful number, since it uses less digits than its factorization.

21643012136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2705376523 (or 2705376519 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 29.

Adding to 21643012136 its reverse (63121034612), we get a palindrome (84764046748).

The spelling of 21643012136 in words is "twenty-one billion, six hundred forty-three million, twelve thousand, one hundred thirty-six".