1306309557721 has 81 divisors (see below), whose sum is σ = 1648620892863. Its totient is φ = 1031936764320.

The previous prime is 1306309557701. The next prime is 1306309557733. The reversal of 1306309557721 is 1277559036031.

The square root of 1306309557721 is 1142939.

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., 1216633266121 + 89676291600 = 1103011^2 + 299460^2 .

It is not a de Polignac number, because 1306309557721 - 2⁷ = 1306309557593 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is not an unprimeable number, because it can be changed into a prime (1306309557701) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 5704408435 + ... + 5704408663.

Almost surely, 2^{1306309557721} is an apocalyptic number.

1306309557721 is the 1142939-th square number.

1306309557721 is the 571470-th centered octagonal number.

It is an amenable number.

1306309557721 is a deficient number, since it is larger than the sum of its proper divisors (342311335142).

1306309557721 is an frugal number, since it uses more digits than its factorization.

1306309557721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 580 (or 290 counting only the distinct ones).

The product of its (nonzero) digits is 1190700, while the sum is 49.

Multiplying 1306309557721 by its sum of digits (49), we get a square (64009168328329 = 8000573²).

1306309557721 divided by its sum of digits (49) gives a square (26659378729 = 163277²).

The spelling of 1306309557721 in words is "one trillion, three hundred six billion, three hundred nine million, five hundred fifty-seven thousand, seven hundred twenty-one".