21561773481 has 8 divisors (see below), whose sum is σ = 31943368160. Its totient is φ = 14374515636.

The previous prime is 21561773479. The next prime is 21561773483. The reversal of 21561773481 is 18437716512.

21561773481 is a `hidden beast` number, since 2 + 1 + 561 + 7 + 7 + 3 + 4 + 81 = 666.

It is an interprime number because it is at equal distance from previous prime (21561773479) and next prime (21561773483).

It is not a de Polignac number, because 21561773481 - 2¹ = 21561773479 is a prime.

It is a super-2 number, since 2×21561773481² (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 (21561773483) 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, 399292075 + ... + 399292128.

It is an arithmetic number, because the mean of its divisors is an integer number (3992921020).

Almost surely, 2^21561773481 is an apocalyptic number.

It is an amenable number.

21561773481 is a deficient number, since it is larger than the sum of its proper divisors (10381594679).

21561773481 is an equidigital number, since it uses as much as digits as its factorization.

21561773481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 798584212 (or 798584206 counting only the distinct ones).

The product of its digits is 282240, while the sum is 45.

The spelling of 21561773481 in words is "twenty-one billion, five hundred sixty-one million, seven hundred seventy-three thousand, four hundred eighty-one".