66587721 has 16 divisors (see below), whose sum is σ = 91872768. Its totient is φ = 42854400.

The previous prime is 66587713. The next prime is 66587771. The reversal of 66587721 is 12778566.

It is not a de Polignac number, because 66587721 - 2³ = 66587713 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66587771) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 59055 + ... + 60171.

It is an arithmetic number, because the mean of its divisors is an integer number (5742048).

Almost surely, 2^66587721 is an apocalyptic number.

It is an amenable number.

66587721 is a deficient number, since it is larger than the sum of its proper divisors (25285047).

66587721 is a wasteful number, since it uses less digits than its factorization.

66587721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1792.

The product of its digits is 141120, while the sum is 42.

The square root of 66587721 is about 8160.1299622004. The cubic root of 66587721 is about 405.3200153215.

The spelling of 66587721 in words is "sixty-six million, five hundred eighty-seven thousand, seven hundred twenty-one".