21581473185 has 12 divisors (see below), whose sum is σ = 37407886932. Its totient is φ = 11510119008.

The previous prime is 21581473129. The next prime is 21581473201. The reversal of 21581473185 is 58137418512.

21581473185 is a `hidden beast` number, since 21 + 5 + 81 + 473 + 1 + 85 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 4956723216 + 16624749969 = 70404^2 + 128937^2 .

It is not a de Polignac number, because 21581473185 - 2⁸ = 21581472929 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 479588293 = 21581473185 / (2 + 1 + 5 + 8 + 1 + 4 + 7 + 3 + 1 + 8 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 21581473185.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 239794102 + ... + 239794191.

It is an arithmetic number, because the mean of its divisors is an integer number (3117323911).

Almost surely, 2^21581473185 is an apocalyptic number.

It is an amenable number.

21581473185 is a deficient number, since it is larger than the sum of its proper divisors (15826413747).

21581473185 is a wasteful number, since it uses less digits than its factorization.

21581473185 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 479588304 (or 479588301 counting only the distinct ones).

The product of its digits is 268800, while the sum is 45.

The spelling of 21581473185 in words is "twenty-one billion, five hundred eighty-one million, four hundred seventy-three thousand, one hundred eighty-five".