21511068421 has 2 divisors, whose sum is σ = 21511068422. Its totient is φ = 21511068420.

The previous prime is 21511068407. The next prime is 21511068427. The reversal of 21511068421 is 12486011512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17500379521 + 4010688900 = 132289^2 + 63330^2 .

It is a cyclic number.

It is not a de Polignac number, because 21511068421 - 2²³ = 21502679813 is a prime.

It is a super-2 number, since 2×21511068421² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21511068427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10755534210 + 10755534211.

It is an arithmetic number, because the mean of its divisors is an integer number (10755534211).

Almost surely, 2^21511068421 is an apocalyptic number.

It is an amenable number.

21511068421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21511068421 is an equidigital number, since it uses as much as digits as its factorization.

21511068421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3840, while the sum is 31.

Adding to 21511068421 its reverse (12486011512), we get a palindrome (33997079933).

The spelling of 21511068421 in words is "twenty-one billion, five hundred eleven million, sixty-eight thousand, four hundred twenty-one".