21115410561 has 40 divisors (see below), whose sum is σ = 36060710400. Its totient is φ = 12061991232.

The previous prime is 21115410539. The next prime is 21115410593. The reversal of 21115410561 is 16501451112.

21115410561 is a `hidden beast` number, since 2 + 111 + 541 + 0 + 5 + 6 + 1 = 666.

It is not a de Polignac number, because 21115410561 - 2¹⁵ = 21115377793 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21115410461) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 3313200 + ... + 3319566.

It is an arithmetic number, because the mean of its divisors is an integer number (901517760).

Almost surely, 2^21115410561 is an apocalyptic number.

21115410561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21115410561 is a deficient number, since it is larger than the sum of its proper divisors (14945299839).

21115410561 is an equidigital number, since it uses as much as digits as its factorization.

21115410561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12235 (or 12226 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 27.

Adding to 21115410561 its reverse (16501451112), we get a palindrome (37616861673).

The spelling of 21115410561 in words is "twenty-one billion, one hundred fifteen million, four hundred ten thousand, five hundred sixty-one".