61211731581 has 96 divisors (see below), whose sum is σ = 125697132288. Its totient is φ = 27625605120.

The previous prime is 61211731573. The next prime is 61211731591. The reversal of 61211731581 is 18513711216.

It is a happy number.

61211731581 is a `hidden beast` number, since 6 + 1 + 2 + 1 + 1 + 73 + 1 + 581 = 666.

It is not a de Polignac number, because 61211731581 - 2³ = 61211731573 is a prime.

It is a super-2 number, since 2×61211731581² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61211731541) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 46686 + ... + 352991.

It is an arithmetic number, because the mean of its divisors is an integer number (1309345128).

Almost surely, 2^61211731581 is an apocalyptic number.

It is an amenable number.

61211731581 is an abundant number, since it is smaller than the sum of its proper divisors (64485400707).

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

61211731581 is a wasteful number, since it uses less digits than its factorization.

61211731581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399731 (or 399728 counting only the distinct ones).

The product of its digits is 10080, while the sum is 36.

The spelling of 61211731581 in words is "sixty-one billion, two hundred eleven million, seven hundred thirty-one thousand, five hundred eighty-one".