21155561075 has 24 divisors (see below), whose sum is σ = 28642953936. Its totient is φ = 15372288000.

The previous prime is 21155561057. The next prime is 21155561083. The reversal of 21155561075 is 57016555112.

It is a happy number.

It is not a de Polignac number, because 21155561075 - 2¹² = 21155556979 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 283715 + ... + 350435.

It is an arithmetic number, because the mean of its divisors is an integer number (1193456414).

Almost surely, 2^21155561075 is an apocalyptic number.

21155561075 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21155561075 is a deficient number, since it is larger than the sum of its proper divisors (7487392861).

21155561075 is a wasteful number, since it uses less digits than its factorization.

21155561075 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67895 (or 67890 counting only the distinct ones).

The product of its (nonzero) digits is 52500, while the sum is 38.

The spelling of 21155561075 in words is "twenty-one billion, one hundred fifty-five million, five hundred sixty-one thousand, seventy-five".