64521640 has 16 divisors (see below), whose sum is σ = 145173780. Its totient is φ = 25808640.

The previous prime is 64521623. The next prime is 64521641. The reversal of 64521640 is 4612546.

It can be written as a sum of positive squares in 2 ways, for example, as 59259204 + 5262436 = 7698^2 + 2294^2 .

It is a junction number, because it is equal to n+sod(n) for n = 64521599 and 64521608.

It is not an unprimeable number, because it can be changed into a prime (64521641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 806481 + ... + 806560.

Almost surely, 2^64521640 is an apocalyptic number.

It is an amenable number.

64521640 is an abundant number, since it is smaller than the sum of its proper divisors (80652140).

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

64521640 is a wasteful number, since it uses less digits than its factorization.

64521640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1613052 (or 1613048 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 64521640 is about 8032.5363366747. The cubic root of 64521640 is about 401.0838107335.

The spelling of 64521640 in words is "sixty-four million, five hundred twenty-one thousand, six hundred forty".