1643209812 has 36 divisors (see below), whose sum is σ = 4265934036. Its totient is φ = 532932480.

The previous prime is 1643209787. The next prime is 1643209819. The reversal of 1643209812 is 2189023461.

1643209812 is a `hidden beast` number, since 1 + 643 + 2 + 0 + 9 + 8 + 1 + 2 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1108490436 + 534719376 = 33294^2 + 23124^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1643209819) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 615489 + ... + 618152.

Almost surely, 2^1643209812 is an apocalyptic number.

1643209812 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

1643209812 is an abundant number, since it is smaller than the sum of its proper divisors (2622724224).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1643209812 is a wasteful number, since it uses less digits than its factorization.

1643209812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1233688 (or 1233683 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 1643209812 is about 40536.5244193431. The cubic root of 1643209812 is about 1180.0425657345.

The spelling of 1643209812 in words is "one billion, six hundred forty-three million, two hundred nine thousand, eight hundred twelve".