21121209719 has 2 divisors, whose sum is σ = 21121209720. Its totient is φ = 21121209718.

The previous prime is 21121209713. The next prime is 21121209743. The reversal of 21121209719 is 91790212112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121209719 is a prime.

It is a super-2 number, since 2×21121209719² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21121209713) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560604859 + 10560604860.

It is an arithmetic number, because the mean of its divisors is an integer number (10560604860).

Almost surely, 2^21121209719 is an apocalyptic number.

21121209719 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121209719 is an equidigital number, since it uses as much as digits as its factorization.

21121209719 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 35.

The spelling of 21121209719 in words is "twenty-one billion, one hundred twenty-one million, two hundred nine thousand, seven hundred nineteen".