11856597821 has 2 divisors, whose sum is σ = 11856597822. Its totient is φ = 11856597820.

The previous prime is 11856597817. The next prime is 11856597847. The reversal of 11856597821 is 12879565811.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11305005625 + 551592196 = 106325^2 + 23486^2 .

It is a cyclic number.

It is not a de Polignac number, because 11856597821 - 2² = 11856597817 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11856597121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5928298910 + 5928298911.

It is an arithmetic number, because the mean of its divisors is an integer number (5928298911).

Almost surely, 2^11856597821 is an apocalyptic number.

It is an amenable number.

11856597821 is a deficient number, since it is larger than the sum of its proper divisors (1).

11856597821 is an equidigital number, since it uses as much as digits as its factorization.

11856597821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1209600, while the sum is 53.

The spelling of 11856597821 in words is "eleven billion, eight hundred fifty-six million, five hundred ninety-seven thousand, eight hundred twenty-one".