1643521551 has 16 divisors (see below), whose sum is σ = 2505828864. Its totient is φ = 938624544.

The previous prime is 1643521549. The next prime is 1643521559. The reversal of 1643521551 is 1551253461.

1643521551 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 1643521551 - 2¹ = 1643521549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1643521559) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17601 + ... + 59973.

It is an arithmetic number, because the mean of its divisors is an integer number (156614304).

Almost surely, 2^1643521551 is an apocalyptic number.

1643521551 is a deficient number, since it is larger than the sum of its proper divisors (862307313).

1643521551 is a wasteful number, since it uses less digits than its factorization.

1643521551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44230.

The product of its digits is 18000, while the sum is 33.

The square root of 1643521551 is about 40540.3693989090. The cubic root of 1643521551 is about 1180.1171843308.

The spelling of 1643521551 in words is "one billion, six hundred forty-three million, five hundred twenty-one thousand, five hundred fifty-one".