21918723417 has 8 divisors (see below), whose sum is σ = 32472182880. Its totient is φ = 14612482260.

The previous prime is 21918723413. The next prime is 21918723419. The reversal of 21918723417 is 71432781912.

21918723417 is a `hidden beast` number, since 219 + 18 + 7 + 2 + 3 + 417 = 666.

It is not a de Polignac number, because 21918723417 - 2² = 21918723413 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21918723413) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 405902259 + ... + 405902312.

It is an arithmetic number, because the mean of its divisors is an integer number (4059022860).

Almost surely, 2^21918723417 is an apocalyptic number.

21918723417 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21918723417 is a deficient number, since it is larger than the sum of its proper divisors (10553459463).

21918723417 is an equidigital number, since it uses as much as digits as its factorization.

21918723417 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 811804580 (or 811804574 counting only the distinct ones).

The product of its digits is 169344, while the sum is 45.

The spelling of 21918723417 in words is "twenty-one billion, nine hundred eighteen million, seven hundred twenty-three thousand, four hundred seventeen".