661421973 has 8 divisors (see below), whose sum is σ = 882366048. Its totient is φ = 440712944.

The previous prime is 661421947. The next prime is 661421987. The reversal of 661421973 is 379124166.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661421973 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661421933) 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 7 ways as a sum of consecutive naturals, for example, 52086 + ... + 63527.

It is an arithmetic number, because the mean of its divisors is an integer number (110295756).

Almost surely, 2^661421973 is an apocalyptic number.

It is an amenable number.

661421973 is a deficient number, since it is larger than the sum of its proper divisors (220944075).

661421973 is a wasteful number, since it uses less digits than its factorization.

661421973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117523.

The product of its digits is 54432, while the sum is 39.

The square root of 661421973 is about 25718.1253788063. The cubic root of 661421973 is about 871.2836000235.

The spelling of 661421973 in words is "six hundred sixty-one million, four hundred twenty-one thousand, nine hundred seventy-three".