1721521361780 has 48 divisors (see below), whose sum is σ = 4115320642944. Its totient is φ = 598790037120.

The previous prime is 1721521361741. The next prime is 1721521361783. The reversal of 1721521361780 is 871631251271.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721521361783) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 170105747 + ... + 170115866.

It is an arithmetic number, because the mean of its divisors is an integer number (85735846728).

Almost surely, 2^{1721521361780} is an apocalyptic number.

1721521361780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1721521361780 is an abundant number, since it is smaller than the sum of its proper divisors (2393799281164).

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

1721521361780 is a wasteful number, since it uses less digits than its factorization.

1721521361780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 340221656 (or 340221654 counting only the distinct ones).

The product of its (nonzero) digits is 141120, while the sum is 44.

The spelling of 1721521361780 in words is "one trillion, seven hundred twenty-one billion, five hundred twenty-one million, three hundred sixty-one thousand, seven hundred eighty".