1643679540 has 60 divisors (see below), whose sum is σ = 5156288676. Its totient is φ = 438314112.

The previous prime is 1643679529. The next prime is 1643679563. The reversal of 1643679540 is 459763461.

1643679540 is a `hidden beast` number, since 1 + 6 + 4 + 36 + 79 + 540 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 646888356 + 996791184 = 25434^2 + 31572^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a super-2 number, since 2×1643679540² = 5403364860429223200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 505689 + ... + 508928.

Almost surely, 2^1643679540 is an apocalyptic number.

1643679540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1643679540 is an abundant number, since it is smaller than the sum of its proper divisors (3512609136).

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

1643679540 is a wasteful number, since it uses less digits than its factorization.

1643679540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1014638 (or 1014627 counting only the distinct ones).

The product of its (nonzero) digits is 544320, while the sum is 45.

The square root of 1643679540 is about 40542.3178913096. The cubic root of 1643679540 is about 1180.1549973548.

The spelling of 1643679540 in words is "one billion, six hundred forty-three million, six hundred seventy-nine thousand, five hundred forty".