21502020017 has 4 divisors (see below), whose sum is σ = 21579644916. Its totient is φ = 21424395120.

The previous prime is 21502019999. The next prime is 21502020061. The reversal of 21502020017 is 71002020512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1335463936 + 20166556081 = 36544^2 + 142009^2 .

It is a cyclic number.

It is not a de Polignac number, because 21502020017 - 2⁶ = 21502019953 is a prime.

It is a super-2 number, since 2×21502020017² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21502020817) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38812034 + ... + 38812587.

It is an arithmetic number, because the mean of its divisors is an integer number (5394911229).

Almost surely, 2^21502020017 is an apocalyptic number.

It is an amenable number.

21502020017 is a deficient number, since it is larger than the sum of its proper divisors (77624899).

21502020017 is an equidigital number, since it uses as much as digits as its factorization.

21502020017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77624898.

The product of its (nonzero) digits is 280, while the sum is 20.

Adding to 21502020017 its reverse (71002020512), we get a palindrome (92504040529).

The spelling of 21502020017 in words is "twenty-one billion, five hundred two million, twenty thousand, seventeen".