21663636394 has 16 divisors (see below), whose sum is σ = 32614403328. Its totient is φ = 10792224432.

The previous prime is 21663636377. The next prime is 21663636403. The reversal of 21663636394 is 49363636612.

It is a super-2 number, since 2×21663636394² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 806667 + ... + 833089.

It is an arithmetic number, because the mean of its divisors is an integer number (2038400208).

Almost surely, 2^21663636394 is an apocalyptic number.

21663636394 is a deficient number, since it is larger than the sum of its proper divisors (10950766934).

21663636394 is a wasteful number, since it uses less digits than its factorization.

21663636394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27909.

The product of its digits is 2519424, while the sum is 49.

The spelling of 21663636394 in words is "twenty-one billion, six hundred sixty-three million, six hundred thirty-six thousand, three hundred ninety-four".