19815228738 has 18 divisors (see below), whose sum is σ = 42934289619. Its totient is φ = 6604877172.

The previous prime is 19815228703. The next prime is 19815228743. The reversal of 19815228738 is 83782251891.

19815228738 is a `hidden beast` number, since 1 + 9 + 8 + 1 + 522 + 87 + 38 = 666.

It can be written as a sum of positive squares in only one way, i.e., 9907614369 + 9907614369 = 99537^2 + 99537^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=99537.

It is a super-2 number, since 2×19815228738² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 580633 + ... + 613811.

Almost surely, 2^19815228738 is an apocalyptic number.

19815228738 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

19815228738 is an abundant number, since it is smaller than the sum of its proper divisors (23119060881).

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

19815228738 is an frugal number, since it uses more digits than its factorization.

19815228738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66366 (or 33184 counting only the distinct ones).

The product of its digits is 1935360, while the sum is 54.

The spelling of 19815228738 in words is "nineteen billion, eight hundred fifteen million, two hundred twenty-eight thousand, seven hundred thirty-eight".