66720381 has 48 divisors (see below), whose sum is σ = 115726464. Its totient is φ = 33291648.

The previous prime is 66720373. The next prime is 66720431. The reversal of 66720381 is 18302766.

It is not a de Polignac number, because 66720381 - 2³ = 66720373 is a prime.

It is a super-2 number, since 2×66720381² = 8903218481570322, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66724381) 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, 98215 + ... + 98891.

It is an arithmetic number, because the mean of its divisors is an integer number (2410968).

Almost surely, 2^66720381 is an apocalyptic number.

It is an amenable number.

66720381 is a deficient number, since it is larger than the sum of its proper divisors (49006083).

66720381 is a wasteful number, since it uses less digits than its factorization.

66720381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738 (or 719 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 66720381 is about 8168.2544646944. The cubic root of 66720381 is about 405.5890042789.

The spelling of 66720381 in words is "sixty-six million, seven hundred twenty thousand, three hundred eighty-one".