21993436906 has 32 divisors (see below), whose sum is σ = 38339688960. Its totient is φ = 9266745600.

The previous prime is 21993436867. The next prime is 21993436921. The reversal of 21993436906 is 60963439912.

It is a super-3 number, since 3×21993436906³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2223151 + ... + 2233021.

It is an arithmetic number, because the mean of its divisors is an integer number (1198115280).

Almost surely, 2^21993436906 is an apocalyptic number.

21993436906 is a deficient number, since it is larger than the sum of its proper divisors (16346252054).

21993436906 is a wasteful number, since it uses less digits than its factorization.

21993436906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12550.

The product of its (nonzero) digits is 1889568, while the sum is 52.

The spelling of 21993436906 in words is "twenty-one billion, nine hundred ninety-three million, four hundred thirty-six thousand, nine hundred six".