1620643521 has 16 divisors (see below), whose sum is σ = 2470175744. Its totient is φ = 925848144.

The previous prime is 1620643489. The next prime is 1620643529. The reversal of 1620643521 is 1253460261.

It is not a de Polignac number, because 1620643521 - 2⁵ = 1620643489 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1620643529) 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, 109086 + ... + 123048.

It is an arithmetic number, because the mean of its divisors is an integer number (154385984).

Almost surely, 2^1620643521 is an apocalyptic number.

It is an amenable number.

1620643521 is a deficient number, since it is larger than the sum of its proper divisors (849532223).

1620643521 is a wasteful number, since it uses less digits than its factorization.

1620643521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19500.

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 1620643521 is about 40257.2170051532. The cubic root of 1620643521 is about 1174.6157840808.

The spelling of 1620643521 in words is "one billion, six hundred twenty million, six hundred forty-three thousand, five hundred twenty-one".