766665421 has 4 divisors (see below), whose sum is σ = 766943100. Its totient is φ = 766387744.

The previous prime is 766665407. The next prime is 766665461. The reversal of 766665421 is 124566667.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 124566667 = 17 ⋅7327451.

It can be written as a sum of positive squares in 2 ways, for example, as 618069321 + 148596100 = 24861^2 + 12190^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-766665421 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (766665461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134656 + ... + 140233.

It is an arithmetic number, because the mean of its divisors is an integer number (191735775).

Almost surely, 2^766665421 is an apocalyptic number.

It is an amenable number.

766665421 is a deficient number, since it is larger than the sum of its proper divisors (277679).

766665421 is a wasteful number, since it uses less digits than its factorization.

766665421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 277678.

The product of its digits is 362880, while the sum is 43.

The square root of 766665421 is about 27688.7237156211. The cubic root of 766665421 is about 915.2406310695.

The spelling of 766665421 in words is "seven hundred sixty-six million, six hundred sixty-five thousand, four hundred twenty-one".