61981784865 has 576 divisors, whose sum is σ = 160906217472. Its totient is φ = 21598617600.

The previous prime is 61981784863. The next prime is 61981784903. The reversal of 61981784865 is 56848718916.

61981784865 is a `hidden beast` number, since 6 + 1 + 9 + 81 + 78 + 486 + 5 = 666.

It is not a de Polignac number, because 61981784865 - 2¹ = 61981784863 is a prime.

It is a super-2 number, since 2×61981784865² (a number of 22 digits) contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (61981784863) by changing a digit.

It is a polite number, since it can be written in 575 ways as a sum of consecutive naturals, for example, 166170819 + ... + 166171191.

It is an arithmetic number, because the mean of its divisors is an integer number (279351072).

Almost surely, 2^61981784865 is an apocalyptic number.

61981784865 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

61981784865 is an abundant number, since it is smaller than the sum of its proper divisors (98924432607).

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

61981784865 is a wasteful number, since it uses less digits than its factorization.

61981784865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 470 (or 460 counting only the distinct ones).

The product of its digits is 23224320, while the sum is 63.

The spelling of 61981784865 in words is "sixty-one billion, nine hundred eighty-one million, seven hundred eighty-four thousand, eight hundred sixty-five".