21155281109 has 2 divisors, whose sum is σ = 21155281110. Its totient is φ = 21155281108.

The previous prime is 21155281099. The next prime is 21155281127. The reversal of 21155281109 is 90118255112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20341034884 + 814246225 = 142622^2 + 28535^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21155281109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21155251109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577640554 + 10577640555.

It is an arithmetic number, because the mean of its divisors is an integer number (10577640555).

Almost surely, 2^21155281109 is an apocalyptic number.

It is an amenable number.

21155281109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155281109 is an equidigital number, since it uses as much as digits as its factorization.

21155281109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7200, while the sum is 35.

The spelling of 21155281109 in words is "twenty-one billion, one hundred fifty-five million, two hundred eighty-one thousand, one hundred nine".