20619781891801 has 9 divisors (see below), whose sum is σ = 20963634179709. Its totient is φ = 20281480226400.

The previous prime is 20619781891781. The next prime is 20619781891829. The reversal of 20619781891801 is 10819818791602.

The square root of 20619781891801 is 4540901.

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

It can be written as a sum of positive squares in 4 ways, for example, as 15900547027401 + 4719234864400 = 3987549^2 + 2172380^2 .

It is not a de Polignac number, because 20619781891801 - 2¹¹ = 20619781889753 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (61).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20619781891801.

It is not an unprimeable number, because it can be changed into a prime (20619781891001) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 276957741 + ... + 277032181.

Almost surely, 2^{20619781891801} is an apocalyptic number.

20619781891801 is the 4540901-st square number.

20619781891801 is the 2270451-st centered octagonal number.

It is an amenable number.

20619781891801 is a deficient number, since it is larger than the sum of its proper divisors (343852287908).

20619781891801 is an frugal number, since it uses more digits than its factorization.

20619781891801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149004 (or 74502 counting only the distinct ones).

The product of its (nonzero) digits is 3483648, while the sum is 61.

The spelling of 20619781891801 in words is "twenty trillion, six hundred nineteen billion, seven hundred eighty-one million, eight hundred ninety-one thousand, eight hundred one".