1281663581 has 12 divisors (see below), whose sum is σ = 1418245500. Its totient is φ = 1157312640.

The previous prime is 1281663577. The next prime is 1281663587. The reversal of 1281663581 is 1853661821.

It can be written as a sum of positive squares in 2 ways, for example, as 47265625 + 1234397956 = 6875^2 + 35134^2 .

It is not a de Polignac number, because 1281663581 - 2² = 1281663577 is a prime.

It is a super-2 number, since 2×1281663581² = 3285323069723487122, which contains 22 as substring.

It is a hoax number, since the sum of its digits (41) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281663587) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17516 + ... + 53573.

It is an arithmetic number, because the mean of its divisors is an integer number (118187125).

Almost surely, 2^1281663581 is an apocalyptic number.

1281663581 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1281663581 is a deficient number, since it is larger than the sum of its proper divisors (136581919).

1281663581 is a wasteful number, since it uses less digits than its factorization.

1281663581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71260 (or 71249 counting only the distinct ones).

The product of its digits is 69120, while the sum is 41.

The square root of 1281663581 is about 35800.3293420605. The cubic root of 1281663581 is about 1086.2372235852.

The spelling of 1281663581 in words is "one billion, two hundred eighty-one million, six hundred sixty-three thousand, five hundred eighty-one".