2001578121 has 21 divisors (see below), whose sum is σ = 3002806551. Its totient is φ = 1333580112.

The previous prime is 2001578107. The next prime is 2001578141. The reversal of 2001578121 is 1218751002.

The square root of 2001578121 is 44739.

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., 637310025 + 1364268096 = 25245^2 + 36936^2 .

It is not a de Polignac number, because 2001578121 - 2⁷ = 2001577993 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (2001578101) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 1207125 + ... + 1208781.

Almost surely, 2^2001578121 is an apocalyptic number.

2001578121 is the 44739-th square number.

2001578121 is the 22370-th centered octagonal number.

It is an amenable number.

2001578121 is a deficient number, since it is larger than the sum of its proper divisors (1001228430).

2001578121 is an frugal number, since it uses more digits than its factorization.

2001578121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3332 (or 1660 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 27.

The cubic root of 2001578121 is about 1260.2523474167.

The spelling of 2001578121 in words is "two billion, one million, five hundred seventy-eight thousand, one hundred twenty-one".