21661013867 has 2 divisors, whose sum is σ = 21661013868. Its totient is φ = 21661013866.

The previous prime is 21661013861. The next prime is 21661013977. The reversal of 21661013867 is 76831016612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21661013867 - 2¹⁴ = 21660997483 is a prime.

It is a super-3 number, since 3×21661013867³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21661013861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830506933 + 10830506934.

It is an arithmetic number, because the mean of its divisors is an integer number (10830506934).

Almost surely, 2^21661013867 is an apocalyptic number.

21661013867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661013867 is an equidigital number, since it uses as much as digits as its factorization.

21661013867 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72576, while the sum is 41.

The spelling of 21661013867 in words is "twenty-one billion, six hundred sixty-one million, thirteen thousand, eight hundred sixty-seven".