261191890 has 16 divisors (see below), whose sum is σ = 481079808. Its totient is φ = 102046896.

The previous prime is 261191881. The next prime is 261191911. The reversal of 261191890 is 98191162.

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, 303282 + ... + 304141.

It is an arithmetic number, because the mean of its divisors is an integer number (30067488).

Almost surely, 2^261191890 is an apocalyptic number.

261191890 is a deficient number, since it is larger than the sum of its proper divisors (219887918).

261191890 is a wasteful number, since it uses less digits than its factorization.

261191890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 607473.

The product of its (nonzero) digits is 7776, while the sum is 37.

The square root of 261191890 is about 16161.4321766358. The cubic root of 261191890 is about 639.2242309383.

The spelling of 261191890 in words is "two hundred sixty-one million, one hundred ninety-one thousand, eight hundred ninety".