201565979521 has 9 divisors (see below), whose sum is σ = 202439374761. Its totient is φ = 200696342064.

The previous prime is 201565979477. The next prime is 201565979591. The reversal of 201565979521 is 125979565102.

The square root of 201565979521 is 448961.

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

It can be written as a sum of positive squares in 4 ways, for example, as 45066619521 + 156499360000 = 212289^2 + 395600^2 .

It is not a de Polignac number, because 201565979521 - 2¹³ = 201565971329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (201565979591) 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, 120769675 + ... + 120771343.

Almost surely, 2^201565979521 is an apocalyptic number.

201565979521 is the 448961-st square number.

201565979521 is the 224481-st centered octagonal number.

It is an amenable number.

201565979521 is a deficient number, since it is larger than the sum of its proper divisors (873395240).

201565979521 is an frugal number, since it uses more digits than its factorization.

201565979521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3876 (or 1938 counting only the distinct ones).

The product of its (nonzero) digits is 1701000, while the sum is 52.

The spelling of 201565979521 in words is "two hundred one billion, five hundred sixty-five million, nine hundred seventy-nine thousand, five hundred twenty-one".