19998767889 has 45 divisors (see below), whose sum is σ = 31567982457. Its totient is φ = 12615527736.

The previous prime is 19998767863. The next prime is 19998767897. The reversal of 19998767889 is 98876789991.

The square root of 19998767889 is 141417.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 19998767889 - 2²³ = 19990379281 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (81).

It is not an unprimeable number, because it can be changed into a prime (19998767849) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 24181894 + ... + 24182720.

Almost surely, 2^19998767889 is an apocalyptic number.

19998767889 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

19998767889 is the 141417-th square number.

19998767889 is the 70709-th centered octagonal number.

It is an amenable number.

19998767889 is a deficient number, since it is larger than the sum of its proper divisors (11569214568).

19998767889 is an frugal number, since it uses more digits than its factorization.

19998767889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1704 (or 849 counting only the distinct ones).

The product of its digits is 987614208, while the sum is 81.

Multiplying 19998767889 by its sum of digits (81), we get a square (1619900199009 = 1272753²).

19998767889 divided by its sum of digits (81) gives a square (246898369 = 15713²).

The spelling of 19998767889 in words is "nineteen billion, nine hundred ninety-eight million, seven hundred sixty-seven thousand, eight hundred eighty-nine".