64245721 has 4 divisors (see below), whose sum is σ = 64526500. Its totient is φ = 63964944.

The previous prime is 64245691. The next prime is 64245743. The reversal of 64245721 is 12754246.

64245721 = T₆₅₄₃ + T₆₅₄₄ + T₆₅₄₅.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 54228496 + 10017225 = 7364^2 + 3165^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64245721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (64245781) 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, 140046 + ... + 140503.

It is an arithmetic number, because the mean of its divisors is an integer number (16131625).

Almost surely, 2^64245721 is an apocalyptic number.

64245721 is the 6545-th centered triangular number.

It is an amenable number.

64245721 is a deficient number, since it is larger than the sum of its proper divisors (280779).

64245721 is a wasteful number, since it uses less digits than its factorization.

64245721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280778.

The product of its digits is 13440, while the sum is 31.

The square root of 64245721 is about 8015.3428498100. The cubic root of 64245721 is about 400.5112649919.

Adding to 64245721 its reverse (12754246), we get a palindrome (76999967).

The spelling of 64245721 in words is "sixty-four million, two hundred forty-five thousand, seven hundred twenty-one".