21075436581 has 8 divisors (see below), whose sum is σ = 28103267904. Its totient is φ = 14048948160.

The previous prime is 21075436531. The next prime is 21075436631. The reversal of 21075436581 is 18563457012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21075436531) and next prime (21075436631).

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

It is not a de Polignac number, because 21075436581 - 2¹⁷ = 21075305509 is a prime.

It is a super-2 number, since 2×21075436581² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21075436531) 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, 298516 + ... + 362301.

It is an arithmetic number, because the mean of its divisors is an integer number (3512908488).

Almost surely, 2^21075436581 is an apocalyptic number.

It is an amenable number.

21075436581 is a deficient number, since it is larger than the sum of its proper divisors (7027831323).

21075436581 is a wasteful number, since it uses less digits than its factorization.

21075436581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 671451.

The product of its (nonzero) digits is 201600, while the sum is 42.

The spelling of 21075436581 in words is "twenty-one billion, seventy-five million, four hundred thirty-six thousand, five hundred eighty-one".