21402179809949 has 2 divisors, whose sum is σ = 21402179809950. Its totient is φ = 21402179809948.

The previous prime is 21402179809931. The next prime is 21402179810021. The reversal of 21402179809949 is 94990897120412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16858537987225 + 4543641822724 = 4105915^2 + 2131582^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21402179809949 is a prime.

It is a super-4 number, since 4×21402179809949⁴ (a number of 54 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

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 (21402179889949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701089904974 + 10701089904975.

It is an arithmetic number, because the mean of its divisors is an integer number (10701089904975).

Almost surely, 2^{21402179809949} is an apocalyptic number.

It is an amenable number.

21402179809949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21402179809949 is an equidigital number, since it uses as much as digits as its factorization.

21402179809949 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23514624, while the sum is 65.

The spelling of 21402179809949 in words is "twenty-one trillion, four hundred two billion, one hundred seventy-nine million, eight hundred nine thousand, nine hundred forty-nine".