81978290 has 8 divisors (see below), whose sum is σ = 147560940. Its totient is φ = 32791312.

The previous prime is 81978287. The next prime is 81978307. The reversal of 81978290 is 9287918.

It can be written as a sum of positive squares in 2 ways, for example, as 71859529 + 10118761 = 8477^2 + 3181^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4098905 + ... + 4098924.

Almost surely, 2^81978290 is an apocalyptic number.

81978290 is a deficient number, since it is larger than the sum of its proper divisors (65582650).

81978290 is a wasteful number, since it uses less digits than its factorization.

81978290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8197836.

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 81978290 is about 9054.1863245683. The cubic root of 81978290 is about 434.4098042606.

The spelling of 81978290 in words is "eighty-one million, nine hundred seventy-eight thousand, two hundred ninety".