634688981 has 4 divisors (see below), whose sum is σ = 635170764. Its totient is φ = 634207200.

The previous prime is 634688963. The next prime is 634689007. The reversal of 634688981 is 189886436.

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 582256900 + 52432081 = 24130^2 + 7241^2 .

It is a cyclic number.

It is not a de Polignac number, because 634688981 - 2⁶ = 634688917 is a prime.

It is a super-2 number, since 2×634688981² = 805660205205636722, 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 (634688941) 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, 238910 + ... + 241551.

It is an arithmetic number, because the mean of its divisors is an integer number (158792691).

Almost surely, 2^634688981 is an apocalyptic number.

It is an amenable number.

634688981 is a deficient number, since it is larger than the sum of its proper divisors (481783).

634688981 is a wasteful number, since it uses less digits than its factorization.

634688981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 481782.

The product of its digits is 1990656, while the sum is 53.

The square root of 634688981 is about 25193.0343746044. The cubic root of 634688981 is about 859.3834507352.

The spelling of 634688981 in words is "six hundred thirty-four million, six hundred eighty-eight thousand, nine hundred eighty-one".