661366420 has 96 divisors (see below), whose sum is σ = 1655168256. Its totient is φ = 218803200.

The previous prime is 661366411. The next prime is 661366423. The reversal of 661366420 is 24663166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661366423) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 201432 + ... + 204688.

It is an arithmetic number, because the mean of its divisors is an integer number (17241336).

Almost surely, 2^661366420 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661366420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (827584128).

661366420 is an abundant number, since it is smaller than the sum of its proper divisors (993801836).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661366420 is a wasteful number, since it uses less digits than its factorization.

661366420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3361 (or 3359 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 34.

The square root of 661366420 is about 25717.0453201763. The cubic root of 661366420 is about 871.2592062300.

The spelling of 661366420 in words is "six hundred sixty-one million, three hundred sixty-six thousand, four hundred twenty".