66531720 has 32 divisors (see below), whose sum is σ = 199595520. Its totient is φ = 17741760.

The previous prime is 66531719. The next prime is 66531779. The reversal of 66531720 is 2713566.

It is a super-3 number, since 3×66531720³ (a number of 24 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 277096 + ... + 277335.

It is an arithmetic number, because the mean of its divisors is an integer number (6237360).

Almost surely, 2^66531720 is an apocalyptic number.

66531720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66531720 is an abundant number, since it is smaller than the sum of its proper divisors (133063800).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66531720 is a wasteful number, since it uses less digits than its factorization.

66531720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 554445 (or 554441 counting only the distinct ones).

The product of its (nonzero) digits is 7560, while the sum is 30.

The square root of 66531720 is about 8156.6978612671. The cubic root of 66531720 is about 405.2063572676.

It can be divided in two parts, 665 and 31720, that added together give a triangular number (32385 = T₂₅₄).

The spelling of 66531720 in words is "sixty-six million, five hundred thirty-one thousand, seven hundred twenty".