21523192581 has 32 divisors (see below), whose sum is σ = 31465313280. Its totient is φ = 12978345600.

The previous prime is 21523192531. The next prime is 21523192583. The reversal of 21523192581 is 18529132512.

It is a happy number.

It is not a de Polignac number, because 21523192581 - 2⁹ = 21523192069 is a prime.

It is a super-2 number, since 2×21523192581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523192583) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6213456 + ... + 6216918.

It is an arithmetic number, because the mean of its divisors is an integer number (983291040).

Almost surely, 2^21523192581 is an apocalyptic number.

It is an amenable number.

21523192581 is a deficient number, since it is larger than the sum of its proper divisors (9942120699).

21523192581 is a wasteful number, since it uses less digits than its factorization.

21523192581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4377.

The product of its digits is 43200, while the sum is 39.

The spelling of 21523192581 in words is "twenty-one billion, five hundred twenty-three million, one hundred ninety-two thousand, five hundred eighty-one".