1645643603 has 4 divisors (see below), whose sum is σ = 1645735560. Its totient is φ = 1645551648.

The previous prime is 1645643591. The next prime is 1645643611. The reversal of 1645643603 is 3063465461.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 3063465461 = 7 ⋅437637923.

It is a cyclic number.

It is not a de Polignac number, because 1645643603 - 2²⁶ = 1578534739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1645643633) 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, 9473 + ... + 58146.

It is an arithmetic number, because the mean of its divisors is an integer number (411433890).

Almost surely, 2^1645643603 is an apocalyptic number.

1645643603 is a deficient number, since it is larger than the sum of its proper divisors (91957).

1645643603 is an equidigital number, since it uses as much as digits as its factorization.

1645643603 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91956.

The product of its (nonzero) digits is 155520, while the sum is 38.

The square root of 1645643603 is about 40566.5330414124. The cubic root of 1645643603 is about 1180.6248732415.

The spelling of 1645643603 in words is "one billion, six hundred forty-five million, six hundred forty-three thousand, six hundred three".