1521672740721 has 27 divisors (see below), whose sum is σ = 2556867792843. Its totient is φ = 869512477680.

The previous prime is 1521672740711. The next prime is 1521672740761. The reversal of 1521672740721 is 1270472761251.

It is a happy number.

The square root of 1521672740721 is 1233561.

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

1521672740721 is a `hidden beast` number, since 1 + 5 + 216 + 7 + 2 + 7 + 407 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 382714212321 + 1138958528400 = 618639^2 + 1067220^2 .

It is not a de Polignac number, because 1521672740721 - 2⁹ = 1521672740209 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1521672740701) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 25875411 + ... + 25934151.

Almost surely, 2^{1521672740721} is an apocalyptic number.

1521672740721 is the 1233561-st square number.

1521672740721 is the 616781-st centered octagonal number.

It is an amenable number.

1521672740721 is a deficient number, since it is larger than the sum of its proper divisors (1035195052122).

1521672740721 is an frugal number, since it uses more digits than its factorization.

1521672740721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117502 (or 58751 counting only the distinct ones).

The product of its (nonzero) digits is 329280, while the sum is 45.

The spelling of 1521672740721 in words is "one trillion, five hundred twenty-one billion, six hundred seventy-two million, seven hundred forty thousand, seven hundred twenty-one".