1921806890 has 16 divisors (see below), whose sum is σ = 3469170600. Its totient is φ = 766518720.

The previous prime is 1921806881. The next prime is 1921806947. The reversal of 1921806890 is 986081291.

It can be written as a sum of positive squares in 4 ways, for example, as 1639197169 + 282609721 = 40487^2 + 16811^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 271841 + ... + 278820.

Almost surely, 2^1921806890 is an apocalyptic number.

1921806890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1921806890 is a deficient number, since it is larger than the sum of its proper divisors (1547363710).

1921806890 is a wasteful number, since it uses less digits than its factorization.

1921806890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 551017.

The product of its (nonzero) digits is 62208, while the sum is 44.

The square root of 1921806890 is about 43838.4179687178. The cubic root of 1921806890 is about 1243.2827709259.

The spelling of 1921806890 in words is "one billion, nine hundred twenty-one million, eight hundred six thousand, eight hundred ninety".