661421515 has 4 divisors (see below), whose sum is σ = 793705824. Its totient is φ = 529137208.

The previous prime is 661421513. The next prime is 661421561. The reversal of 661421515 is 515124166.

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

It is a cyclic number.

It is not a de Polignac number, because 661421515 - 2¹ = 661421513 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661421513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66142147 + ... + 66142156.

It is an arithmetic number, because the mean of its divisors is an integer number (198426456).

Almost surely, 2^661421515 is an apocalyptic number.

661421515 is a deficient number, since it is larger than the sum of its proper divisors (132284309).

661421515 is a wasteful number, since it uses less digits than its factorization.

661421515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132284308.

The product of its digits is 7200, while the sum is 31.

The square root of 661421515 is about 25718.1164745788. The cubic root of 661421515 is about 871.2833989174.

The spelling of 661421515 in words is "six hundred sixty-one million, four hundred twenty-one thousand, five hundred fifteen".