21121202177 has 2 divisors, whose sum is σ = 21121202178. Its totient is φ = 21121202176.

The previous prime is 21121202171. The next prime is 21121202279. The reversal of 21121202177 is 77120212112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16443189361 + 4678012816 = 128231^2 + 68396^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121202177 - 2¹² = 21121198081 is a prime.

It is a super-2 number, since 2×21121202177² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21121202171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560601088 + 10560601089.

It is an arithmetic number, because the mean of its divisors is an integer number (10560601089).

Almost surely, 2^21121202177 is an apocalyptic number.

It is an amenable number.

21121202177 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121202177 is an equidigital number, since it uses as much as digits as its factorization.

21121202177 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 784, while the sum is 26.

Adding to 21121202177 its reverse (77120212112), we get a palindrome (98241414289).

The spelling of 21121202177 in words is "twenty-one billion, one hundred twenty-one million, two hundred two thousand, one hundred seventy-seven".