1920643639 has 4 divisors (see below), whose sum is σ = 1986872760. Its totient is φ = 1854414520.

The previous prime is 1920643603. The next prime is 1920643661. The reversal of 1920643639 is 9363460291.

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 1920643639 - 2¹⁷ = 1920512567 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1920643595 and 1920643604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1920640639) 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, 33114517 + ... + 33114574.

It is an arithmetic number, because the mean of its divisors is an integer number (496718190).

Almost surely, 2^1920643639 is an apocalyptic number.

1920643639 is a deficient number, since it is larger than the sum of its proper divisors (66229121).

1920643639 is an equidigital number, since it uses as much as digits as its factorization.

1920643639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66229120.

The product of its (nonzero) digits is 209952, while the sum is 43.

The square root of 1920643639 is about 43825.1484766452. The cubic root of 1920643639 is about 1243.0318713111.

The spelling of 1920643639 in words is "one billion, nine hundred twenty million, six hundred forty-three thousand, six hundred thirty-nine".