21106638361 has 2 divisors, whose sum is σ = 21106638362. Its totient is φ = 21106638360.

The previous prime is 21106638283. The next prime is 21106638389. The reversal of 21106638361 is 16383660112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13299855625 + 7806782736 = 115325^2 + 88356^2 .

It is a cyclic number.

It is not a de Polignac number, because 21106638361 - 2²¹ = 21104541209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21106638361.

It is not a weakly prime, because it can be changed into another prime (21106638391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553319180 + 10553319181.

It is an arithmetic number, because the mean of its divisors is an integer number (10553319181).

Almost surely, 2^21106638361 is an apocalyptic number.

It is an amenable number.

21106638361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21106638361 is an equidigital number, since it uses as much as digits as its factorization.

21106638361 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 37.

The spelling of 21106638361 in words is "twenty-one billion, one hundred six million, six hundred thirty-eight thousand, three hundred sixty-one".