666778437 has 48 divisors (see below), whose sum is σ = 1103055408. Its totient is φ = 384491520.

The previous prime is 666778433. The next prime is 666778459. The reversal of 666778437 is 734877666.

It can be written as a sum of positive squares in 8 ways, for example, as 1602756 + 665175681 = 1266^2 + 25791^2 .

It is not a de Polignac number, because 666778437 - 2² = 666778433 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666778433) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 558313 + ... + 559505.

It is an arithmetic number, because the mean of its divisors is an integer number (22980321).

Almost surely, 2^666778437 is an apocalyptic number.

It is an amenable number.

666778437 is a deficient number, since it is larger than the sum of its proper divisors (436276971).

666778437 is a wasteful number, since it uses less digits than its factorization.

666778437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1510 (or 1507 counting only the distinct ones).

The product of its digits is 7112448, while the sum is 54.

The square root of 666778437 is about 25822.0533072024. The cubic root of 666778437 is about 873.6292821981.

The spelling of 666778437 in words is "six hundred sixty-six million, seven hundred seventy-eight thousand, four hundred thirty-seven".