1781623220101 has 4 divisors (see below), whose sum is σ = 1782394821900. Its totient is φ = 1780851618304.

The previous prime is 1781623220093. The next prime is 1781623220131. The reversal of 1781623220101 is 1010223261871.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1429112657025 + 352510563076 = 1195455^2 + 593726^2 .

It is a cyclic number.

It is not a de Polignac number, because 1781623220101 - 2³ = 1781623220093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781623220131) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 385797436 + ... + 385802053.

It is an arithmetic number, because the mean of its divisors is an integer number (445598705475).

Almost surely, 2^{1781623220101} is an apocalyptic number.

It is an amenable number.

1781623220101 is a deficient number, since it is larger than the sum of its proper divisors (771601799).

1781623220101 is an equidigital number, since it uses as much as digits as its factorization.

1781623220101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 771601798.

The product of its (nonzero) digits is 8064, while the sum is 34.

Adding to 1781623220101 its reverse (1010223261871), we get a palindrome (2791846481972).

The spelling of 1781623220101 in words is "one trillion, seven hundred eighty-one billion, six hundred twenty-three million, two hundred twenty thousand, one hundred one".