21655193009 has 2 divisors, whose sum is σ = 21655193010. Its totient is φ = 21655193008.

The previous prime is 21655192957. The next prime is 21655193023. The reversal of 21655193009 is 90039155612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15900453409 + 5754739600 = 126097^2 + 75860^2 .

It is a cyclic number.

It is not a de Polignac number, because 21655193009 - 2¹² = 21655188913 is a prime.

It is not a weakly prime, because it can be changed into another prime (21655193909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827596504 + 10827596505.

It is an arithmetic number, because the mean of its divisors is an integer number (10827596505).

Almost surely, 2^21655193009 is an apocalyptic number.

It is an amenable number.

21655193009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655193009 is an equidigital number, since it uses as much as digits as its factorization.

21655193009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72900, while the sum is 41.

The spelling of 21655193009 in words is "twenty-one billion, six hundred fifty-five million, one hundred ninety-three thousand, nine".