997608781 has 4 divisors (see below), whose sum is σ = 1074347932. Its totient is φ = 920869632.

The previous prime is 997608769. The next prime is 997608797. The reversal of 997608781 is 187806799.

It is the 12895-th star number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 405659881 + 591948900 = 20141^2 + 24330^2 .

It is a cyclic number.

It is not a de Polignac number, because 997608781 - 2²³ = 989220173 is a prime.

It is a super-2 number, since 2×997608781² = 1990446559856611922, 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 (997603781) 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, 38369556 + ... + 38369581.

It is an arithmetic number, because the mean of its divisors is an integer number (268586983).

Almost surely, 2^997608781 is an apocalyptic number.

It is an amenable number.

997608781 is a deficient number, since it is larger than the sum of its proper divisors (76739151).

997608781 is a wasteful number, since it uses less digits than its factorization.

997608781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76739150.

The product of its (nonzero) digits is 1524096, while the sum is 55.

The square root of 997608781 is about 31584.9454804025. The cubic root of 997608781 is about 999.2022908293.

The spelling of 997608781 in words is "nine hundred ninety-seven million, six hundred eight thousand, seven hundred eighty-one".