1605123921 has 32 divisors (see below), whose sum is σ = 2268269568. Its totient is φ = 1008184320.

The previous prime is 1605123913. The next prime is 1605123943. The reversal of 1605123921 is 1293215061.

It is not a de Polignac number, because 1605123921 - 2³ = 1605123913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1605123991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 674085 + ... + 676461.

It is an arithmetic number, because the mean of its divisors is an integer number (70883424).

Almost surely, 2^1605123921 is an apocalyptic number.

It is an amenable number.

1605123921 is a deficient number, since it is larger than the sum of its proper divisors (663145647).

1605123921 is a wasteful number, since it uses less digits than its factorization.

1605123921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2601.

The product of its (nonzero) digits is 3240, while the sum is 30.

The square root of 1605123921 is about 40063.9978159943. The cubic root of 1605123921 is about 1170.8543011838.

Adding to 1605123921 its reverse (1293215061), we get a palindrome (2898338982).

The spelling of 1605123921 in words is "one billion, six hundred five million, one hundred twenty-three thousand, nine hundred twenty-one".