21151718444 has 12 divisors (see below), whose sum is σ = 39192890184. Its totient is φ = 9953749824.

The previous prime is 21151718443. The next prime is 21151718473. The reversal of 21151718444 is 44481715112.

It is a super-2 number, since 2×21151718444² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21151718398 and 21151718407.

It is not an unprimeable number, because it can be changed into a prime (21151718443) 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 3 ways as a sum of consecutive naturals, for example, 155527274 + ... + 155527409.

It is an arithmetic number, because the mean of its divisors is an integer number (3266074182).

Almost surely, 2^21151718444 is an apocalyptic number.

It is an amenable number.

21151718444 is a deficient number, since it is larger than the sum of its proper divisors (18041171740).

21151718444 is a wasteful number, since it uses less digits than its factorization.

21151718444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 311054704 (or 311054702 counting only the distinct ones).

The product of its digits is 35840, while the sum is 38.

The spelling of 21151718444 in words is "twenty-one billion, one hundred fifty-one million, seven hundred eighteen thousand, four hundred forty-four".