61661988864 has 432 divisors, whose sum is σ = 210465637200. Its totient is φ = 17337729024.

The previous prime is 61661988781. The next prime is 61661989057. The reversal of 61661988864 is 46888916616.

61661988864 is a `hidden beast` number, since 6 + 1 + 6 + 619 + 8 + 8 + 8 + 6 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 60511747 + ... + 60512765.

It is an arithmetic number, because the mean of its divisors is an integer number (487188975).

Almost surely, 2^61661988864 is an apocalyptic number.

61661988864 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 61661988864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105232818600).

61661988864 is an abundant number, since it is smaller than the sum of its proper divisors (148803648336).

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

61661988864 is a wasteful number, since it uses less digits than its factorization.

61661988864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1128 (or 1098 counting only the distinct ones).

The product of its digits is 23887872, while the sum is 63.

It can be divided in two parts, 61661 and 988864, that added together give a triangular number (1050525 = T₁₄₄₉).

The spelling of 61661988864 in words is "sixty-one billion, six hundred sixty-one million, nine hundred eighty-eight thousand, eight hundred sixty-four".