21516404323 has 2 divisors, whose sum is σ = 21516404324. Its totient is φ = 21516404322.

The previous prime is 21516404303. The next prime is 21516404341. The reversal of 21516404323 is 32340461512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21516404323 - 2¹³ = 21516396131 is a prime.

It is not a weakly prime, because it can be changed into another prime (21516404303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758202161 + 10758202162.

It is an arithmetic number, because the mean of its divisors is an integer number (10758202162).

Almost surely, 2^21516404323 is an apocalyptic number.

21516404323 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516404323 is an equidigital number, since it uses as much as digits as its factorization.

21516404323 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 31.

Adding to 21516404323 its reverse (32340461512), we get a palindrome (53856865835).

The spelling of 21516404323 in words is "twenty-one billion, five hundred sixteen million, four hundred four thousand, three hundred twenty-three".