66838821 has 32 divisors (see below), whose sum is σ = 106487808. Its totient is φ = 36486720.

The previous prime is 66838817. The next prime is 66838843. The reversal of 66838821 is 12883866.

It is not a de Polignac number, because 66838821 - 2² = 66838817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66838861) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 53415 + ... + 54651.

It is an arithmetic number, because the mean of its divisors is an integer number (3327744).

Almost surely, 2^66838821 is an apocalyptic number.

It is an amenable number.

66838821 is a deficient number, since it is larger than the sum of its proper divisors (39648987).

66838821 is a wasteful number, since it uses less digits than its factorization.

66838821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1361.

The product of its digits is 110592, while the sum is 42.

The square root of 66838821 is about 8175.5012690354. The cubic root of 66838821 is about 405.8288588469.

The spelling of 66838821 in words is "sixty-six million, eight hundred thirty-eight thousand, eight hundred twenty-one".