21187228609 has 2 divisors, whose sum is σ = 21187228610. Its totient is φ = 21187228608.

The previous prime is 21187228591. The next prime is 21187228649. The reversal of 21187228609 is 90682278112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17096347009 + 4090881600 = 130753^2 + 63960^2 .

It is a cyclic number.

It is not a de Polignac number, because 21187228609 - 2⁵ = 21187228577 is a prime.

It is a super-2 number, since 2×21187228609² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21187228649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10593614304 + 10593614305.

It is an arithmetic number, because the mean of its divisors is an integer number (10593614305).

Almost surely, 2^21187228609 is an apocalyptic number.

It is an amenable number.

21187228609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21187228609 is an equidigital number, since it uses as much as digits as its factorization.

21187228609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 193536, while the sum is 46.

The spelling of 21187228609 in words is "twenty-one billion, one hundred eighty-seven million, two hundred twenty-eight thousand, six hundred nine".