61721787906 has 24 divisors (see below), whose sum is σ = 138341939580. Its totient is φ = 19864483296.

The previous prime is 61721787889. The next prime is 61721787949. The reversal of 61721787906 is 60978712716.

61721787906 is a `hidden beast` number, since 617 + 2 + 17 + 8 + 7 + 9 + 0 + 6 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 61558075881 + 163712025 = 248109^2 + 12795^2 .

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59119965 + ... + 59121008.

Almost surely, 2^61721787906 is an apocalyptic number.

61721787906 is an abundant number, since it is smaller than the sum of its proper divisors (76620151674).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

61721787906 is a wasteful number, since it uses less digits than its factorization.

61721787906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118241010 (or 118241007 counting only the distinct ones).

The product of its (nonzero) digits is 1778112, while the sum is 54.

The spelling of 61721787906 in words is "sixty-one billion, seven hundred twenty-one million, seven hundred eighty-seven thousand, nine hundred six".