21896605666 has 24 divisors (see below), whose sum is σ = 35655593364. Its totient is φ = 10080607680.

The previous prime is 21896605657. The next prime is 21896605681. The reversal of 21896605666 is 66650669812.

It can be written as a sum of positive squares in 6 ways, for example, as 688800025 + 21207805641 = 26245^2 + 145629^2 .

It is a super-2 number, since 2×21896605666² (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 11 ways as a sum of consecutive naturals, for example, 52596 + ... + 215776.

Almost surely, 2^21896605666 is an apocalyptic number.

21896605666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21896605666 is a deficient number, since it is larger than the sum of its proper divisors (13758987698).

21896605666 is a wasteful number, since it uses less digits than its factorization.

21896605666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163606 (or 163593 counting only the distinct ones).

The product of its (nonzero) digits is 5598720, while the sum is 55.

The spelling of 21896605666 in words is "twenty-one billion, eight hundred ninety-six million, six hundred five thousand, six hundred sixty-six".