2187981 has 6 divisors (see below), whose sum is σ = 3160430. Its totient is φ = 1458648.

The previous prime is 2187979. The next prime is 2188001. The reversal of 2187981 is 1897812.

It can be written as a sum of positive squares in only one way, i.e., 1602756 + 585225 = 1266^2 + 765^2 .

It is not a de Polignac number, because 2187981 - 2¹ = 2187979 is a prime.

It is a super-2 number, since 2×2187981² = 9574521712722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2187901) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 121546 + ... + 121563.

2^2187981 is an apocalyptic number.

It is an amenable number.

2187981 is a deficient number, since it is larger than the sum of its proper divisors (972449).

2187981 is a wasteful number, since it uses less digits than its factorization.

2187981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243115 (or 243112 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 2187981 is about 1479.1825445157. The cubic root of 2187981 is about 129.8218664763.

The spelling of 2187981 in words is "two million, one hundred eighty-seven thousand, nine hundred eighty-one".