21615545046665 has 4 divisors (see below), whose sum is σ = 25938654056004. Its totient is φ = 17292436037328.

The previous prime is 21615545046653. The next prime is 21615545046703. The reversal of 21615545046665 is 56664054551612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10586557182601 + 11028987864064 = 3253699^2 + 3320992^2 .

It is a cyclic number.

It is not a de Polignac number, because 21615545046665 - 2⁸ = 21615545046409 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21615545046665.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2161554504662 + ... + 2161554504671.

It is an arithmetic number, because the mean of its divisors is an integer number (6484663514001).

Almost surely, 2^{21615545046665} is an apocalyptic number.

It is an amenable number.

21615545046665 is a deficient number, since it is larger than the sum of its proper divisors (4323109009339).

21615545046665 is an equidigital number, since it uses as much as digits as its factorization.

21615545046665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4323109009338.

The product of its (nonzero) digits is 25920000, while the sum is 56.

The spelling of 21615545046665 in words is "twenty-one trillion, six hundred fifteen billion, five hundred forty-five million, forty-six thousand, six hundred sixty-five".