61811721818 has 128 divisors (see below), whose sum is σ = 123301232640. Its totient is φ = 22527933120.

The previous prime is 61811721809. The next prime is 61811721821. The reversal of 61811721818 is 81812711816.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 47437355 + ... + 47438657.

It is an arithmetic number, because the mean of its divisors is an integer number (963290880).

Almost surely, 2^61811721818 is an apocalyptic number.

61811721818 is a deficient number, since it is larger than the sum of its proper divisors (61489510822).

61811721818 is a wasteful number, since it uses less digits than its factorization.

61811721818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1632.

The product of its digits is 43008, while the sum is 44.

The spelling of 61811721818 in words is "sixty-one billion, eight hundred eleven million, seven hundred twenty-one thousand, eight hundred eighteen".