521423666 has 4 divisors (see below), whose sum is σ = 782135502. Its totient is φ = 260711832.

The previous prime is 521423659. The next prime is 521423717. The reversal of 521423666 is 666324125.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 451350025 + 70073641 = 21245^2 + 8371^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130355915 + ... + 130355918.

Almost surely, 2^521423666 is an apocalyptic number.

521423666 is a deficient number, since it is larger than the sum of its proper divisors (260711836).

521423666 is a wasteful number, since it uses less digits than its factorization.

521423666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260711835.

The product of its digits is 51840, while the sum is 35.

The square root of 521423666 is about 22834.7031073321. The cubic root of 521423666 is about 804.8783510222.

The spelling of 521423666 in words is "five hundred twenty-one million, four hundred twenty-three thousand, six hundred sixty-six".