21147211917 has 32 divisors (see below), whose sum is σ = 33915893760. Its totient is φ = 12945493440.

The previous prime is 21147211909. The next prime is 21147211927. The reversal of 21147211917 is 71911274112.

It is a happy number.

It is not a de Polignac number, because 21147211917 - 2³ = 21147211909 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147211927) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 90678 + ... + 224759.

It is an arithmetic number, because the mean of its divisors is an integer number (1059871680).

Almost surely, 2^21147211917 is an apocalyptic number.

21147211917 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21147211917 is a deficient number, since it is larger than the sum of its proper divisors (12768681843).

21147211917 is a wasteful number, since it uses less digits than its factorization.

21147211917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315650 (or 315644 counting only the distinct ones).

The product of its digits is 7056, while the sum is 36.

The spelling of 21147211917 in words is "twenty-one billion, one hundred forty-seven million, two hundred eleven thousand, nine hundred seventeen".