281980021 has 4 divisors (see below), whose sum is σ = 291703500. Its totient is φ = 272256544.

The previous prime is 281980009. The next prime is 281980031. The reversal of 281980021 is 120089182.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 175271121 + 106708900 = 13239^2 + 10330^2 .

It is a cyclic number.

It is not a de Polignac number, because 281980021 - 2¹⁷ = 281848949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (281980031) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4861696 + ... + 4861753.

It is an arithmetic number, because the mean of its divisors is an integer number (72925875).

Almost surely, 2^281980021 is an apocalyptic number.

It is an amenable number.

281980021 is a deficient number, since it is larger than the sum of its proper divisors (9723479).

281980021 is an equidigital number, since it uses as much as digits as its factorization.

281980021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9723478.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 281980021 is about 16792.2607471418. The cubic root of 281980021 is about 655.7517317580.

The spelling of 281980021 in words is "two hundred eighty-one million, nine hundred eighty thousand, twenty-one".