21355351646665 has 16 divisors (see below), whose sum is σ = 26741179358208. Its totient is φ = 16341141125056.

The previous prime is 21355351646627. The next prime is 21355351646687. The reversal of 21355351646665 is 56664615355312.

It is a cyclic number.

It is not a de Polignac number, because 21355351646665 - 2²⁵ = 21355318092233 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3570567 + ... + 7447123.

It is an arithmetic number, because the mean of its divisors is an integer number (1671323709888).

Almost surely, 2^{21355351646665} is an apocalyptic number.

It is an amenable number.

21355351646665 is a deficient number, since it is larger than the sum of its proper divisors (5385827711543).

21355351646665 is a wasteful number, since it uses less digits than its factorization.

21355351646665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3924488.

The product of its digits is 58320000, while the sum is 58.

The spelling of 21355351646665 in words is "twenty-one trillion, three hundred fifty-five billion, three hundred fifty-one million, six hundred forty-six thousand, six hundred sixty-five".