64721015 has 4 divisors (see below), whose sum is σ = 77665224. Its totient is φ = 51776808.

The previous prime is 64721009. The next prime is 64721047. The reversal of 64721015 is 51012746.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 51012746 = 2 ⋅25506373.

It is a cyclic number.

It is not a de Polignac number, because 64721015 - 2⁶ = 64720951 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 6472097 + ... + 6472106.

It is an arithmetic number, because the mean of its divisors is an integer number (19416306).

Almost surely, 2^64721015 is an apocalyptic number.

64721015 is a deficient number, since it is larger than the sum of its proper divisors (12944209).

64721015 is a wasteful number, since it uses less digits than its factorization.

64721015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12944208.

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 64721015 is about 8044.9372278471. The cubic root of 64721015 is about 401.4965087549.

The spelling of 64721015 in words is "sixty-four million, seven hundred twenty-one thousand, fifteen".