66631815 has 48 divisors (see below), whose sum is σ = 120845088. Its totient is φ = 35220096.

The previous prime is 66631813. The next prime is 66631837. The reversal of 66631815 is 51813666.

It is a happy number.

It is not a de Polignac number, because 66631815 - 2¹ = 66631813 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66631815.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66631813) 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, 210037 + ... + 210353.

It is an arithmetic number, because the mean of its divisors is an integer number (2517606).

Almost surely, 2^66631815 is an apocalyptic number.

66631815 is a deficient number, since it is larger than the sum of its proper divisors (54213273).

66631815 is a wasteful number, since it uses less digits than its factorization.

66631815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 510 (or 498 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 66631815 is about 8162.8313102746. The cubic root of 66631815 is about 405.4094624297.

The spelling of 66631815 in words is "sixty-six million, six hundred thirty-one thousand, eight hundred fifteen".