1643215661 has 8 divisors (see below), whose sum is σ = 1712858400. Its totient is φ = 1574438320.

The previous prime is 1643215649. The next prime is 1643215663. The reversal of 1643215661 is 1665123461.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1643215661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1643215663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 212471 + ... + 220068.

It is an arithmetic number, because the mean of its divisors is an integer number (214107300).

Almost surely, 2^1643215661 is an apocalyptic number.

It is an amenable number.

1643215661 is a deficient number, since it is larger than the sum of its proper divisors (69642739).

1643215661 is a wasteful number, since it uses less digits than its factorization.

1643215661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 432699.

The product of its digits is 25920, while the sum is 35.

The square root of 1643215661 is about 40536.5965640926. The cubic root of 1643215661 is about 1180.0439658520.

The spelling of 1643215661 in words is "one billion, six hundred forty-three million, two hundred fifteen thousand, six hundred sixty-one".