661309890 has 16 divisors (see below), whose sum is σ = 1587143808. Its totient is φ = 176349296.

The previous prime is 661309889. The next prime is 661309921. The reversal of 661309890 is 98903166.

661309890 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×661309890² = 874661541223624200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11021802 + ... + 11021861.

It is an arithmetic number, because the mean of its divisors is an integer number (99196488).

Almost surely, 2^661309890 is an apocalyptic number.

661309890 is an abundant number, since it is smaller than the sum of its proper divisors (925833918).

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

661309890 is a wasteful number, since it uses less digits than its factorization.

661309890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22043673.

The product of its (nonzero) digits is 69984, while the sum is 42.

The square root of 661309890 is about 25715.9462201957. The cubic root of 661309890 is about 871.2343820253.

The spelling of 661309890 in words is "six hundred sixty-one million, three hundred nine thousand, eight hundred ninety".