11921216921 has 2 divisors, whose sum is σ = 11921216922. Its totient is φ = 11921216920.

The previous prime is 11921216903. The next prime is 11921216927. The reversal of 11921216921 is 12961212911.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11521016896 + 400200025 = 107336^2 + 20005^2 .

It is a cyclic number.

It is not a de Polignac number, because 11921216921 - 2²² = 11917022617 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (11921216927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5960608460 + 5960608461.

It is an arithmetic number, because the mean of its divisors is an integer number (5960608461).

Almost surely, 2^11921216921 is an apocalyptic number.

It is an amenable number.

11921216921 is a deficient number, since it is larger than the sum of its proper divisors (1).

11921216921 is an equidigital number, since it uses as much as digits as its factorization.

11921216921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 35.

The spelling of 11921216921 in words is "eleven billion, nine hundred twenty-one million, two hundred sixteen thousand, nine hundred twenty-one".