1921561663890 has 64 divisors (see below), whose sum is σ = 5031193191552. Its totient is φ = 465815040000.

The previous prime is 1921561663859. The next prime is 1921561663913. The reversal of 1921561663890 is 983661651291.

It is a Smith number, since the sum of its digits (57) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 1921561663890.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9680640 + ... + 9877140.

It is an arithmetic number, because the mean of its divisors is an integer number (78612393618).

Almost surely, 2^{1921561663890} is an apocalyptic number.

1921561663890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1921561663890 is an abundant number, since it is smaller than the sum of its proper divisors (3109631527662).

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

1921561663890 is a wasteful number, since it uses less digits than its factorization.

1921561663890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226155.

The product of its (nonzero) digits is 4199040, while the sum is 57.

The spelling of 1921561663890 in words is "one trillion, nine hundred twenty-one billion, five hundred sixty-one million, six hundred sixty-three thousand, eight hundred ninety".