21605640607777 has 16 divisors (see below), whose sum is σ = 22684129643520. Its totient is φ = 20538753306192.

The previous prime is 21605640607741. The next prime is 21605640607843. The reversal of 21605640607777 is 77770604650612.

It is a cyclic number.

It is not a de Polignac number, because 21605640607777 - 2³⁵ = 21571280869409 is a prime.

It is a super-3 number, since 3×21605640607777³ (a number of 41 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21605640697777) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 127527558 + ... + 127696864.

It is an arithmetic number, because the mean of its divisors is an integer number (1417758102720).

Almost surely, 2^{21605640607777} is an apocalyptic number.

It is an amenable number.

21605640607777 is a deficient number, since it is larger than the sum of its proper divisors (1078489035743).

21605640607777 is a wasteful number, since it uses less digits than its factorization.

21605640607777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203532.

The product of its (nonzero) digits is 20744640, while the sum is 58.

The spelling of 21605640607777 in words is "twenty-one trillion, six hundred five billion, six hundred forty million, six hundred seven thousand, seven hundred seventy-seven".