261399890 has 8 divisors (see below), whose sum is σ = 470519820. Its totient is φ = 104559952.

The previous prime is 261399883. The next prime is 261399907. The reversal of 261399890 is 98993162.

261399890 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 240157009 + 21242881 = 15497^2 + 4609^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13069985 + ... + 13070004.

Almost surely, 2^261399890 is an apocalyptic number.

261399890 is a deficient number, since it is larger than the sum of its proper divisors (209119930).

261399890 is a wasteful number, since it uses less digits than its factorization.

261399890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26139996.

The product of its (nonzero) digits is 209952, while the sum is 47.

The square root of 261399890 is about 16167.8659692614. The cubic root of 261399890 is about 639.3938678565.

The spelling of 261399890 in words is "two hundred sixty-one million, three hundred ninety-nine thousand, eight hundred ninety".