661398144 has 128 divisors (see below), whose sum is σ = 1978767360. Its totient is φ = 193920000.

The previous prime is 661398121. The next prime is 661398149. The reversal of 661398144 is 441893166.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-3 number, since 3×661398144³ (a number of 27 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 661398096 and 661398105.

It is not an unprimeable number, because it can be changed into a prime (661398149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 128419 + ... + 133469.

It is an arithmetic number, because the mean of its divisors is an integer number (15459120).

Almost surely, 2^661398144 is an apocalyptic number.

661398144 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661398144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (989383680).

661398144 is an abundant number, since it is smaller than the sum of its proper divisors (1317369216).

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

661398144 is a wasteful number, since it uses less digits than its factorization.

661398144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5110 (or 5098 counting only the distinct ones).

The product of its digits is 124416, while the sum is 42.

The square root of 661398144 is about 25717.6621021430. The cubic root of 661398144 is about 871.2731366748.

The spelling of 661398144 in words is "six hundred sixty-one million, three hundred ninety-eight thousand, one hundred forty-four".