661520649 has 8 divisors (see below), whose sum is σ = 882642880. Its totient is φ = 440706096.

The previous prime is 661520647. The next prime is 661520689. The reversal of 661520649 is 946025166.

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

It is not a de Polignac number, because 661520649 - 2¹ = 661520647 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (661520647) 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, 71854 + ... + 80535.

It is an arithmetic number, because the mean of its divisors is an integer number (110330360).

Almost surely, 2^661520649 is an apocalyptic number.

It is an amenable number.

661520649 is a deficient number, since it is larger than the sum of its proper divisors (221122231).

661520649 is a wasteful number, since it uses less digits than its factorization.

661520649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153839.

The product of its (nonzero) digits is 77760, while the sum is 39.

The square root of 661520649 is about 25720.0437208027. The cubic root of 661520649 is about 871.3269261244.

The spelling of 661520649 in words is "six hundred sixty-one million, five hundred twenty thousand, six hundred forty-nine".