21665190481 has 9 divisors (see below), whose sum is σ = 23815584219. Its totient is φ = 19694155800.

The previous prime is 21665190467. The next prime is 21665190497. The reversal of 21665190481 is 18409156612.

The square root of 21665190481 is 147191.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 2637746881 + 19027443600 = 51359^2 + 137940^2 .

It is not a de Polignac number, because 21665190481 - 2¹³ = 21665182289 is a prime.

It is a super-2 number, since 2×21665190481² (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 (21665190431) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1612411 + ... + 1625791.

Almost surely, 2^21665190481 is an apocalyptic number.

21665190481 is the 147191-st square number.

21665190481 is the 73596-th centered octagonal number.

It is an amenable number.

21665190481 is a deficient number, since it is larger than the sum of its proper divisors (2150393738).

21665190481 is an frugal number, since it uses more digits than its factorization.

21665190481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26784 (or 13392 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 43.

The spelling of 21665190481 in words is "twenty-one billion, six hundred sixty-five million, one hundred ninety thousand, four hundred eighty-one".