1620555553 has 4 divisors (see below), whose sum is σ = 1635701040. Its totient is φ = 1605410068.

The previous prime is 1620555539. The next prime is 1620555593. The reversal of 1620555553 is 3555550261.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 3555550261 = 37 ⋅96095953.

It is a cyclic number.

It is not a de Polignac number, because 1620555553 - 2²⁵ = 1587001121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1620555593) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7572583 + ... + 7572796.

It is an arithmetic number, because the mean of its divisors is an integer number (408925260).

Almost surely, 2^1620555553 is an apocalyptic number.

It is an amenable number.

1620555553 is a deficient number, since it is larger than the sum of its proper divisors (15145487).

1620555553 is a wasteful number, since it uses less digits than its factorization.

1620555553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15145486.

The product of its (nonzero) digits is 112500, while the sum is 37.

The square root of 1620555553 is about 40256.1244160438. The cubic root of 1620555553 is about 1174.5945311095.

The spelling of 1620555553 in words is "one billion, six hundred twenty million, five hundred fifty-five thousand, five hundred fifty-three".