1251981 has 6 divisors (see below), whose sum is σ = 1808430. Its totient is φ = 834648.

The previous prime is 1251961. The next prime is 1251983. The reversal of 1251981 is 1891521.

It can be written as a sum of positive squares in only one way, i.e., 1232100 + 19881 = 1110^2 + 141^2 .

It is not a de Polignac number, because 1251981 - 2¹³ = 1243789 is a prime.

It is a super-2 number, since 2×1251981² = 3134912848722, which contains 22 as substring.

1251981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1251983) 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, 69546 + ... + 69563.

It is an arithmetic number, because the mean of its divisors is an integer number (301405).

2^1251981 is an apocalyptic number.

It is an amenable number.

1251981 is a deficient number, since it is larger than the sum of its proper divisors (556449).

1251981 is a wasteful number, since it uses less digits than its factorization.

1251981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139115 (or 139112 counting only the distinct ones).

The product of its digits is 720, while the sum is 27.

The square root of 1251981 is about 1118.9195681549. The cubic root of 1251981 is about 107.7786102682.

The spelling of 1251981 in words is "one million, two hundred fifty-one thousand, nine hundred eighty-one".