1643500451 has 4 divisors (see below), whose sum is σ = 1647050592. Its totient is φ = 1639950312.

The previous prime is 1643500427. The next prime is 1643500471. The reversal of 1643500451 is 1540053461.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1643500451 - 2³⁰ = 569758627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1643500471) 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, 1774376 + ... + 1775301.

It is an arithmetic number, because the mean of its divisors is an integer number (411762648).

Almost surely, 2^1643500451 is an apocalyptic number.

1643500451 is a deficient number, since it is larger than the sum of its proper divisors (3550141).

1643500451 is an equidigital number, since it uses as much as digits as its factorization.

1643500451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3550140.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 1643500451 is about 40540.1091636419. The cubic root of 1643500451 is about 1180.1121340818.

The spelling of 1643500451 in words is "one billion, six hundred forty-three million, five hundred thousand, four hundred fifty-one".