1620521605 has 8 divisors (see below), whose sum is σ = 1954702872. Its totient is φ = 1289699328.

The previous prime is 1620521593. The next prime is 1620521611. The reversal of 1620521605 is 5061250261.

It can be written as a sum of positive squares in 4 ways, for example, as 170511364 + 1450010241 = 13058^2 + 38079^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1620521605 - 2⁹ = 1620521093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 838684 + ... + 840613.

It is an arithmetic number, because the mean of its divisors is an integer number (244337859).

Almost surely, 2^1620521605 is an apocalyptic number.

It is an amenable number.

1620521605 is a deficient number, since it is larger than the sum of its proper divisors (334181267).

1620521605 is a wasteful number, since it uses less digits than its factorization.

1620521605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1679495.

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 1620521605 is about 40255.7027637079. The cubic root of 1620521605 is about 1174.5863291046.

Adding to 1620521605 its reverse (5061250261), we get a palindrome (6681771866).

It can be divided in two parts, 16 and 20521605, that added together give a triangular number (20521621 = T₆₄₀₆).

The spelling of 1620521605 in words is "one billion, six hundred twenty million, five hundred twenty-one thousand, six hundred five".