661869390 has 256 divisors, whose sum is σ = 2080899072. Its totient is φ = 130927104.

The previous prime is 661869343. The next prime is 661869401. The reversal of 661869390 is 93968166.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 5211507 + ... + 5211633.

It is an arithmetic number, because the mean of its divisors is an integer number (8128512).

Almost surely, 2^661869390 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661869390, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1040449536).

661869390 is an abundant number, since it is smaller than the sum of its proper divisors (1419029682).

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

661869390 is a wasteful number, since it uses less digits than its factorization.

661869390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263.

The product of its (nonzero) digits is 419904, while the sum is 48.

The square root of 661869390 is about 25726.8223844298. The cubic root of 661869390 is about 871.4800148410.

The spelling of 661869390 in words is "six hundred sixty-one million, eight hundred sixty-nine thousand, three hundred ninety".