21664233381 has 12 divisors (see below), whose sum is σ = 33013192992. Its totient is φ = 12379176504.

The previous prime is 21664233343. The next prime is 21664233391. The reversal of 21664233381 is 18333246612.

It is not a de Polignac number, because 21664233381 - 2⁶ = 21664233317 is a prime.

It is a super-2 number, since 2×21664233381² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664233391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 658440 + ... + 690558.

It is an arithmetic number, because the mean of its divisors is an integer number (2751099416).

Almost surely, 2^21664233381 is an apocalyptic number.

21664233381 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21664233381 is a deficient number, since it is larger than the sum of its proper divisors (11348959611).

21664233381 is an frugal number, since it uses more digits than its factorization.

21664233381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64248 (or 32129 counting only the distinct ones).

The product of its digits is 124416, while the sum is 39.

Adding to 21664233381 its reverse (18333246612), we get a palindrome (39997479993).

The spelling of 21664233381 in words is "twenty-one billion, six hundred sixty-four million, two hundred thirty-three thousand, three hundred eighty-one".