781220021101 has 4 divisors (see below), whose sum is σ = 841313868892. Its totient is φ = 721126173312.

The previous prime is 781220021089. The next prime is 781220021117. The reversal of 781220021101 is 101120022187.

It is a happy number.

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 80900424900 + 700319596201 = 284430^2 + 836851^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-781220021101 is a prime.

It is a super-2 number, since 2×781220021101² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (781220021191) 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, 30046923876 + ... + 30046923901.

It is an arithmetic number, because the mean of its divisors is an integer number (210328467223).

Almost surely, 2^781220021101 is an apocalyptic number.

It is an amenable number.

781220021101 is a deficient number, since it is larger than the sum of its proper divisors (60093847791).

781220021101 is a wasteful number, since it uses less digits than its factorization.

781220021101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60093847790.

The product of its (nonzero) digits is 448, while the sum is 25.

Adding to 781220021101 its reverse (101120022187), we get a palindrome (882340043288).

The spelling of 781220021101 in words is "seven hundred eighty-one billion, two hundred twenty million, twenty-one thousand, one hundred one".