21720441097 has 8 divisors (see below), whose sum is σ = 22139641160. Its totient is φ = 21304529280.

The previous prime is 21720441089. The next prime is 21720441133. The reversal of 21720441097 is 79014402712.

It can be written as a sum of positive squares in 4 ways, for example, as 368217721 + 21352223376 = 19189^2 + 146124^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21720441097 - 2³ = 21720441089 is a prime.

It is a super-2 number, since 2×21720441097² (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 (21720441037) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 808722 + ... + 835147.

It is an arithmetic number, because the mean of its divisors is an integer number (2767455145).

Almost surely, 2^21720441097 is an apocalyptic number.

It is an amenable number.

21720441097 is a deficient number, since it is larger than the sum of its proper divisors (419200063).

21720441097 is a wasteful number, since it uses less digits than its factorization.

21720441097 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1644123.

The product of its (nonzero) digits is 28224, while the sum is 37.

The spelling of 21720441097 in words is "twenty-one billion, seven hundred twenty million, four hundred forty-one thousand, ninety-seven".