1551661959780 has 144 divisors (see below), whose sum is σ = 4871741238000. Its totient is φ = 399284121600.

The previous prime is 1551661959779. The next prime is 1551661959791. The reversal of 1551661959780 is 879591661551.

1551661959780 is a `hidden beast` number, since 1 + 5 + 5 + 1 + 6 + 619 + 5 + 9 + 7 + 8 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 3384446976 + 1548277512804 = 58176^2 + 1244298^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 9318696 + ... + 9483744.

It is an arithmetic number, because the mean of its divisors is an integer number (33831536375).

Almost surely, 2^{1551661959780} is an apocalyptic number.

1551661959780 is a gapful number since it is divisible by the number (10) 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 1551661959780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2435870619000).

1551661959780 is an abundant number, since it is smaller than the sum of its proper divisors (3320079278220).

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

1551661959780 is a wasteful number, since it uses less digits than its factorization.

1551661959780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166894 (or 166889 counting only the distinct ones).

The product of its (nonzero) digits is 20412000, while the sum is 63.

The spelling of 1551661959780 in words is "one trillion, five hundred fifty-one billion, six hundred sixty-one million, nine hundred fifty-nine thousand, seven hundred eighty".