661605420 has 96 divisors (see below), whose sum is σ = 2190182400. Its totient is φ = 146006784.

The previous prime is 661605407. The next prime is 661605421. The reversal of 661605420 is 24506166.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (661605421) 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, 14980 + ... + 39339.

It is an arithmetic number, because the mean of its divisors is an integer number (22814400).

Almost surely, 2^661605420 is an apocalyptic number.

661605420 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661605420 is an abundant number, since it is smaller than the sum of its proper divisors (1528576980).

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

661605420 is a wasteful number, since it uses less digits than its factorization.

661605420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54367 (or 54365 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 661605420 is about 25721.6916239971. The cubic root of 661605420 is about 871.3641434560.

The spelling of 661605420 in words is "six hundred sixty-one million, six hundred five thousand, four hundred twenty".