66687021 has 6 divisors (see below), whose sum is σ = 96325710. Its totient is φ = 44458008.

The previous prime is 66687011. The next prime is 66687053. The reversal of 66687021 is 12078666.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 39501225 + 27185796 = 6285^2 + 5214^2 .

It is not a de Polignac number, because 66687021 - 2⁶ = 66686957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66687011) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3704826 + ... + 3704843.

It is an arithmetic number, because the mean of its divisors is an integer number (16054285).

Almost surely, 2^66687021 is an apocalyptic number.

It is an amenable number.

66687021 is a deficient number, since it is larger than the sum of its proper divisors (29638689).

66687021 is a wasteful number, since it uses less digits than its factorization.

66687021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7409675 (or 7409672 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 66687021 is about 8166.2121574204. The cubic root of 66687021 is about 405.5213952281.

It can be divided in two parts, 6668 and 7021, that added together give a square (13689 = 117²).

The spelling of 66687021 in words is "sixty-six million, six hundred eighty-seven thousand, twenty-one".