66651421520 has 80 divisors (see below), whose sum is σ = 162337824000. Its totient is φ = 25415330304.

The previous prime is 66651421513. The next prime is 66651421531. The reversal of 66651421520 is 2512415666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×66651421520² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1451 + ... + 365109.

It is an arithmetic number, because the mean of its divisors is an integer number (2029222800).

Almost surely, 2^66651421520 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66651421520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (81168912000).

66651421520 is an abundant number, since it is smaller than the sum of its proper divisors (95686402480).

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

66651421520 is a wasteful number, since it uses less digits than its factorization.

66651421520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363780 (or 363774 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 38.

The spelling of 66651421520 in words is "sixty-six billion, six hundred fifty-one million, four hundred twenty-one thousand, five hundred twenty".