1285499981 has 4 divisors (see below), whose sum is σ = 1286161500. Its totient is φ = 1284838464.

The previous prime is 1285499977. The next prime is 1285499983. The reversal of 1285499981 is 1899945821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1899945821 = 107 ⋅17756503.

It can be written as a sum of positive squares in 2 ways, for example, as 1208674756 + 76825225 = 34766^2 + 8765^2 .

It is a cyclic number.

It is not a de Polignac number, because 1285499981 - 2² = 1285499977 is a prime.

It is a super-2 number, since 2×1285499981² = 3305020402302000722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1285499983) 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, 327836 + ... + 331733.

It is an arithmetic number, because the mean of its divisors is an integer number (321540375).

Almost surely, 2^1285499981 is an apocalyptic number.

It is an amenable number.

1285499981 is a deficient number, since it is larger than the sum of its proper divisors (661519).

1285499981 is an equidigital number, since it uses as much as digits as its factorization.

1285499981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 661518.

The product of its digits is 1866240, while the sum is 56.

The square root of 1285499981 is about 35853.8698190307. The cubic root of 1285499981 is about 1087.3199542688.

The spelling of 1285499981 in words is "one billion, two hundred eighty-five million, four hundred ninety-nine thousand, nine hundred eighty-one".