21001011217165 has 16 divisors (see below), whose sum is σ = 28801462701312. Its totient is φ = 14400655461504.

The previous prime is 21001011217127. The next prime is 21001011217201. The reversal of 21001011217165 is 56171211010012.

It is a cyclic number.

It is not a de Polignac number, because 21001011217165 - 2¹⁵ = 21001011184397 is a prime.

It is a congruent number.

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, 21673072 + ... + 22621318.

It is an arithmetic number, because the mean of its divisors is an integer number (1800091418832).

Almost surely, 2^{21001011217165} is an apocalyptic number.

It is an amenable number.

21001011217165 is a deficient number, since it is larger than the sum of its proper divisors (7800451484147).

21001011217165 is an equidigital number, since it uses as much as digits as its factorization.

21001011217165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1581036.

The product of its (nonzero) digits is 840, while the sum is 28.

Adding to 21001011217165 its reverse (56171211010012), we get a palindrome (77172222227177).

The spelling of 21001011217165 in words is "twenty-one trillion, one billion, eleven million, two hundred seventeen thousand, one hundred sixty-five".