65721520 has 20 divisors (see below), whose sum is σ = 152802720. Its totient is φ = 26288576.

The previous prime is 65721499. The next prime is 65721533. The reversal of 65721520 is 2512756.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×65721520² = 8638636382220800, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 410680 + ... + 410839.

It is an arithmetic number, because the mean of its divisors is an integer number (7640136).

Almost surely, 2^65721520 is an apocalyptic number.

It is an amenable number.

65721520 is an abundant number, since it is smaller than the sum of its proper divisors (87081200).

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

65721520 is a wasteful number, since it uses less digits than its factorization.

65721520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 821532 (or 821526 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 65721520 is about 8106.8810278676. The cubic root of 65721520 is about 403.5548146463.

The spelling of 65721520 in words is "sixty-five million, seven hundred twenty-one thousand, five hundred twenty".