21696840644 has 12 divisors (see below), whose sum is σ = 38003289744. Its totient is φ = 10838757864.

The previous prime is 21696840643. The next prime is 21696840667. The reversal of 21696840644 is 44604869612.

It is a super-2 number, since 2×21696840644² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21696840592 and 21696840601.

It is not an unprimeable number, because it can be changed into a prime (21696840643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2410562 + ... + 2419545.

It is an arithmetic number, because the mean of its divisors is an integer number (3166940812).

Almost surely, 2^21696840644 is an apocalyptic number.

It is an amenable number.

21696840644 is a deficient number, since it is larger than the sum of its proper divisors (16306449100).

21696840644 is a wasteful number, since it uses less digits than its factorization.

21696840644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4831234 (or 4831232 counting only the distinct ones).

The product of its (nonzero) digits is 1990656, while the sum is 50.

The spelling of 21696840644 in words is "twenty-one billion, six hundred ninety-six million, eight hundred forty thousand, six hundred forty-four".