1620736542665 has 4 divisors (see below), whose sum is σ = 1944883851204. Its totient is φ = 1296589234128.

The previous prime is 1620736542661. The next prime is 1620736542671. The reversal of 1620736542665 is 5662456370261.

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 184180880569 + 1436555662096 = 429163^2 + 1198564^2 .

It is a cyclic number.

It is not a de Polignac number, because 1620736542665 - 2² = 1620736542661 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1620736542661) 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 3 ways as a sum of consecutive naturals, for example, 162073654262 + ... + 162073654271.

It is an arithmetic number, because the mean of its divisors is an integer number (486220962801).

Almost surely, 2^{1620736542665} is an apocalyptic number.

It is an amenable number.

1620736542665 is a deficient number, since it is larger than the sum of its proper divisors (324147308539).

1620736542665 is an equidigital number, since it uses as much as digits as its factorization.

1620736542665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 324147308538.

The product of its (nonzero) digits is 10886400, while the sum is 53.

The spelling of 1620736542665 in words is "one trillion, six hundred twenty billion, seven hundred thirty-six million, five hundred forty-two thousand, six hundred sixty-five".