21804371217 has 6 divisors (see below), whose sum is σ = 31495202882. Its totient is φ = 14536247472.

The previous prime is 21804371131. The next prime is 21804371219. The reversal of 21804371217 is 71217340812.

21804371217 is a `hidden beast` number, since 2 + 1 + 8 + 0 + 437 + 1 + 217 = 666.

It can be written as a sum of positive squares in only one way, i.e., 21797274321 + 7096896 = 147639^2 + 2664^2 .

It is not a de Polignac number, because 21804371217 - 2²⁴ = 21787594001 is a prime.

It is a super-2 number, since 2×21804371217² (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 (21804371219) 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, 1211353948 + ... + 1211353965.

Almost surely, 2^21804371217 is an apocalyptic number.

It is an amenable number.

21804371217 is a deficient number, since it is larger than the sum of its proper divisors (9690831665).

21804371217 is a wasteful number, since it uses less digits than its factorization.

21804371217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2422707919 (or 2422707916 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The spelling of 21804371217 in words is "twenty-one billion, eight hundred four million, three hundred seventy-one thousand, two hundred seventeen".