61809906861 has 6 divisors (see below), whose sum is σ = 89280976590. Its totient is φ = 41206604568.

The previous prime is 61809906857. The next prime is 61809906877. The reversal of 61809906861 is 16860990816.

It can be written as a sum of positive squares in only one way, i.e., 51526730025 + 10283176836 = 226995^2 + 101406^2 .

It is not a de Polignac number, because 61809906861 - 2² = 61809906857 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 61809906798 and 61809906807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61809906461) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3433883706 + ... + 3433883723.

It is an arithmetic number, because the mean of its divisors is an integer number (14880162765).

Almost surely, 2^61809906861 is an apocalyptic number.

It is an amenable number.

61809906861 is a deficient number, since it is larger than the sum of its proper divisors (27471069729).

61809906861 is a wasteful number, since it uses less digits than its factorization.

61809906861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6867767435 (or 6867767432 counting only the distinct ones).

The product of its (nonzero) digits is 1119744, while the sum is 54.

The spelling of 61809906861 in words is "sixty-one billion, eight hundred nine million, nine hundred six thousand, eight hundred sixty-one".