21155144051561 has 48 divisors (see below), whose sum is σ = 24288765662592. Its totient is φ = 18379051891200.

The previous prime is 21155144051557. The next prime is 21155144051579. The reversal of 21155144051561 is 16515044155112.

It is not a de Polignac number, because 21155144051561 - 2² = 21155144051557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21155144051551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 119370626 + ... + 119547716.

It is an arithmetic number, because the mean of its divisors is an integer number (506015951304).

Almost surely, 2^{21155144051561} is an apocalyptic number.

It is an amenable number.

21155144051561 is a deficient number, since it is larger than the sum of its proper divisors (3133621611031).

21155144051561 is a wasteful number, since it uses less digits than its factorization.

21155144051561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177634 (or 177621 counting only the distinct ones).

The product of its (nonzero) digits is 120000, while the sum is 41.

The spelling of 21155144051561 in words is "twenty-one trillion, one hundred fifty-five billion, one hundred forty-four million, fifty-one thousand, five hundred sixty-one".