21151718723 has 2 divisors, whose sum is σ = 21151718724. Its totient is φ = 21151718722.

The previous prime is 21151718647. The next prime is 21151718741. The reversal of 21151718723 is 32781715112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21151718723 - 2²⁰ = 21150670147 is a prime.

It is a super-3 number, since 3×21151718723³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21151711723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10575859361 + 10575859362.

It is an arithmetic number, because the mean of its divisors is an integer number (10575859362).

Almost surely, 2^21151718723 is an apocalyptic number.

21151718723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21151718723 is an equidigital number, since it uses as much as digits as its factorization.

21151718723 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23520, while the sum is 38.

The spelling of 21151718723 in words is "twenty-one billion, one hundred fifty-one million, seven hundred eighteen thousand, seven hundred twenty-three".