661860221 has 8 divisors (see below), whose sum is σ = 722381088. Its totient is φ = 601398000.

The previous prime is 661860217. The next prime is 661860223. The reversal of 661860221 is 122068166.

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 661860221 - 2² = 661860217 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661860223) 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, 10886 + ... + 37976.

It is an arithmetic number, because the mean of its divisors is an integer number (90297636).

Almost surely, 2^661860221 is an apocalyptic number.

It is an amenable number.

661860221 is a deficient number, since it is larger than the sum of its proper divisors (60520867).

661860221 is a wasteful number, since it uses less digits than its factorization.

661860221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29323.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 661860221 is about 25726.6441845803. The cubic root of 661860221 is about 871.4759905641.

The spelling of 661860221 in words is "six hundred sixty-one million, eight hundred sixty thousand, two hundred twenty-one".