661981247 has 8 divisors (see below), whose sum is σ = 664304400. Its totient is φ = 659663424.

The previous prime is 661981219. The next prime is 661981249. The reversal of 661981247 is 742189166.

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

It is a cyclic number.

It is not a de Polignac number, because 661981247 - 2¹⁸ = 661719103 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661981198 and 661981207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661981249) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 585779 + ... + 586907.

It is an arithmetic number, because the mean of its divisors is an integer number (83038050).

Almost surely, 2^661981247 is an apocalyptic number.

661981247 is a deficient number, since it is larger than the sum of its proper divisors (2323153).

661981247 is a wasteful number, since it uses less digits than its factorization.

661981247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2665.

The product of its digits is 145152, while the sum is 44.

The square root of 661981247 is about 25728.9962299348. The cubic root of 661981247 is about 871.5291059208.

The spelling of 661981247 in words is "six hundred sixty-one million, nine hundred eighty-one thousand, two hundred forty-seven".