1605213021 has 16 divisors (see below), whose sum is σ = 2158507008. Its totient is φ = 1061070000.

The previous prime is 1605213019. The next prime is 1605213023. The reversal of 1605213021 is 1203125061.

It is an interprime number because it is at equal distance from previous prime (1605213019) and next prime (1605213023).

It is not a de Polignac number, because 1605213021 - 2¹ = 1605213019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1605213023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 166236 + ... + 175626.

It is an arithmetic number, because the mean of its divisors is an integer number (134906688).

Almost surely, 2^1605213021 is an apocalyptic number.

It is an amenable number.

1605213021 is a deficient number, since it is larger than the sum of its proper divisors (553293987).

1605213021 is a wasteful number, since it uses less digits than its factorization.

1605213021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9872.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 1605213021 is about 40065.1097714707. The cubic root of 1605213021 is about 1170.8759653861.

Adding to 1605213021 its reverse (1203125061), we get a palindrome (2808338082).

The spelling of 1605213021 in words is "one billion, six hundred five million, two hundred thirteen thousand, twenty-one".