64691521 has 2 divisors, whose sum is σ = 64691522. Its totient is φ = 64691520.

The previous prime is 64691507. The next prime is 64691527. The reversal of 64691521 is 12519646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 34386496 + 30305025 = 5864^2 + 5505^2 .

It is a cyclic number.

It is not a de Polignac number, because 64691521 - 2⁹ = 64691009 is a prime.

It is not a weakly prime, because it can be changed into another prime (64691527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32345760 + 32345761.

It is an arithmetic number, because the mean of its divisors is an integer number (32345761).

Almost surely, 2^64691521 is an apocalyptic number.

It is an amenable number.

64691521 is a deficient number, since it is larger than the sum of its proper divisors (1).

64691521 is an equidigital number, since it uses as much as digits as its factorization.

64691521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 34.

The square root of 64691521 is about 8043.1039406438. The cubic root of 64691521 is about 401.4355108586.

The spelling of 64691521 in words is "sixty-four million, six hundred ninety-one thousand, five hundred twenty-one".