1201678556521 has 9 divisors (see below), whose sum is σ = 1276543384311. Its totient is φ = 1130974043232.

The previous prime is 1201678556501. The next prime is 1201678556531. The reversal of 1201678556521 is 1256558761021.

The square root of 1201678556521 is 1096211.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 935562890025 + 266115666496 = 967245^2 + 515864^2 .

It is not a de Polignac number, because 1201678556521 - 2⁹ = 1201678556009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1201678556501) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 18603346 + ... + 18667828.

Almost surely, 2^{1201678556521} is an apocalyptic number.

1201678556521 is the 1096211-st square number.

1201678556521 is the 548106-th centered octagonal number.

It is an amenable number.

1201678556521 is a deficient number, since it is larger than the sum of its proper divisors (74864827790).

1201678556521 is an frugal number, since it uses more digits than its factorization.

1201678556521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129000 (or 64500 counting only the distinct ones).

The product of its (nonzero) digits is 1008000, while the sum is 49.

Multiplying 1201678556521 by its sum of digits (49), we get a square (58882249269529 = 7673477²).

The spelling of 1201678556521 in words is "one trillion, two hundred one billion, six hundred seventy-eight million, five hundred fifty-six thousand, five hundred twenty-one".