21008215017 has 6 divisors (see below), whose sum is σ = 30345199482. Its totient is φ = 14005476672.

The previous prime is 21008214979. The next prime is 21008215027. The reversal of 21008215017 is 71051280012.

It can be written as a sum of positive squares in only one way, i.e., 16143989481 + 4864225536 = 127059^2 + 69744^2 .

It is not a de Polignac number, because 21008215017 - 2¹¹ = 21008212969 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21008215027) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1167123048 + ... + 1167123065.

It is an arithmetic number, because the mean of its divisors is an integer number (5057533247).

Almost surely, 2^21008215017 is an apocalyptic number.

It is an amenable number.

21008215017 is a deficient number, since it is larger than the sum of its proper divisors (9336984465).

21008215017 is a wasteful number, since it uses less digits than its factorization.

21008215017 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2334246119 (or 2334246116 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 27.

Adding to 21008215017 its reverse (71051280012), we get a palindrome (92059495029).

The spelling of 21008215017 in words is "twenty-one billion, eight million, two hundred fifteen thousand, seventeen".