81249961 has 12 divisors (see below), whose sum is σ = 91810368. Its totient is φ = 71735664.

The previous prime is 81249943. The next prime is 81249979. The reversal of 81249961 is 16994218.

It is an interprime number because it is at equal distance from previous prime (81249943) and next prime (81249979).

It is not a de Polignac number, because 81249961 - 2⁹ = 81249449 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81249911) 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, 6565 + ... + 14338.

It is an arithmetic number, because the mean of its divisors is an integer number (7650864).

Almost surely, 2^81249961 is an apocalyptic number.

It is an amenable number.

81249961 is a deficient number, since it is larger than the sum of its proper divisors (10560407).

81249961 is a wasteful number, since it uses less digits than its factorization.

81249961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20952 (or 20939 counting only the distinct ones).

The product of its digits is 31104, while the sum is 40.

The square root of 81249961 is about 9013.8760253289. The cubic root of 81249961 is about 433.1194833713.

The spelling of 81249961 in words is "eighty-one million, two hundred forty-nine thousand, nine hundred sixty-one".