261428666 has 4 divisors (see below), whose sum is σ = 392143002. Its totient is φ = 130714332.

The previous prime is 261428641. The next prime is 261428683. The reversal of 261428666 is 666824162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 666824162 = 2 ⋅333412081.

It can be written as a sum of positive squares in only one way, i.e., 212722225 + 48706441 = 14585^2 + 6979^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65357165 + ... + 65357168.

Almost surely, 2^261428666 is an apocalyptic number.

261428666 is a deficient number, since it is larger than the sum of its proper divisors (130714336).

261428666 is a wasteful number, since it uses less digits than its factorization.

261428666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130714335.

The product of its digits is 165888, while the sum is 41.

The square root of 261428666 is about 16168.7558581358. The cubic root of 261428666 is about 639.4173293849.

The spelling of 261428666 in words is "two hundred sixty-one million, four hundred twenty-eight thousand, six hundred sixty-six".