2551581 has 30 divisors (see below), whose sum is σ = 4086170. Its totient is φ = 1586304.

The previous prime is 2551559. The next prime is 2551603. The reversal of 2551581 is 1851552.

It is an interprime number because it is at equal distance from previous prime (2551559) and next prime (2551603).

It can be written as a sum of positive squares in 3 ways, for example, as 1285956 + 1265625 = 1134^2 + 1125^2 .

It is not a de Polignac number, because 2551581 - 2⁹ = 2551069 is a prime.

It is a super-2 number, since 2×2551581² = 13021131199122, which contains 22 as substring.

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

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2551501) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 23355 + ... + 23463.

2^2551581 is an apocalyptic number.

It is an amenable number.

2551581 is a deficient number, since it is larger than the sum of its proper divisors (1534589).

2551581 is a wasteful number, since it uses less digits than its factorization.

2551581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155 (or 129 counting only the distinct ones).

The product of its digits is 2000, while the sum is 27.

The square root of 2551581 is about 1597.3668958633. The cubic root of 2551581 is about 136.6479497139.

The spelling of 2551581 in words is "two million, five hundred fifty-one thousand, five hundred eighty-one".