19287961921 has 2 divisors, whose sum is σ = 19287961922. Its totient is φ = 19287961920.

The previous prime is 19287961859. The next prime is 19287961991. The reversal of 19287961921 is 12916978291.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18254982321 + 1032979600 = 135111^2 + 32140^2 .

It is a cyclic number.

It is not a de Polignac number, because 19287961921 - 2⁹ = 19287961409 is a prime.

It is not a weakly prime, because it can be changed into another prime (19287961991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9643980960 + 9643980961.

It is an arithmetic number, because the mean of its divisors is an integer number (9643980961).

Almost surely, 2^19287961921 is an apocalyptic number.

It is an amenable number.

19287961921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19287961921 is an equidigital number, since it uses as much as digits as its factorization.

19287961921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 979776, while the sum is 55.

The spelling of 19287961921 in words is "nineteen billion, two hundred eighty-seven million, nine hundred sixty-one thousand, nine hundred twenty-one".