21123031819 has 2 divisors, whose sum is σ = 21123031820. Its totient is φ = 21123031818.

The previous prime is 21123031799. The next prime is 21123031843. The reversal of 21123031819 is 91813032112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123031819 is a prime.

It is a super-2 number, since 2×21123031819² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21123031849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561515909 + 10561515910.

It is an arithmetic number, because the mean of its divisors is an integer number (10561515910).

Almost surely, 2^21123031819 is an apocalyptic number.

21123031819 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123031819 is an equidigital number, since it uses as much as digits as its factorization.

21123031819 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 31.

It can be divided in two parts, 211230 and 31819, that added together give a square (243049 = 493²).

The spelling of 21123031819 in words is "twenty-one billion, one hundred twenty-three million, thirty-one thousand, eight hundred nineteen".