81190649 has 4 divisors (see below), whose sum is σ = 82027764. Its totient is φ = 80353536.

The previous prime is 81190631. The next prime is 81190651. The reversal of 81190649 is 94609118.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 94609118 = 2 ⋅47304559.

It can be written as a sum of positive squares in 2 ways, for example, as 28729600 + 52461049 = 5360^2 + 7243^2 .

It is a cyclic number.

It is not a de Polignac number, because 81190649 - 2⁸ = 81190393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81190609) 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, 418412 + ... + 418605.

It is an arithmetic number, because the mean of its divisors is an integer number (20506941).

Almost surely, 2^81190649 is an apocalyptic number.

It is an amenable number.

81190649 is a deficient number, since it is larger than the sum of its proper divisors (837115).

81190649 is an equidigital number, since it uses as much as digits as its factorization.

81190649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 837114.

The product of its (nonzero) digits is 15552, while the sum is 38.

The square root of 81190649 is about 9010.5853860890. The cubic root of 81190649 is about 433.0140661461.

The spelling of 81190649 in words is "eighty-one million, one hundred ninety thousand, six hundred forty-nine".