21785608667 has 2 divisors, whose sum is σ = 21785608668. Its totient is φ = 21785608666.

The previous prime is 21785608657. The next prime is 21785608693. The reversal of 21785608667 is 76680658712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21785608667 - 2²⁴ = 21768831451 is a prime.

It is a super-2 number, since 2×21785608667² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21785608627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10892804333 + 10892804334.

It is an arithmetic number, because the mean of its divisors is an integer number (10892804334).

Almost surely, 2^21785608667 is an apocalyptic number.

21785608667 is a deficient number, since it is larger than the sum of its proper divisors (1).

21785608667 is an equidigital number, since it uses as much as digits as its factorization.

21785608667 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6773760, while the sum is 56.

The spelling of 21785608667 in words is "twenty-one billion, seven hundred eighty-five million, six hundred eight thousand, six hundred sixty-seven".