661521563 has 2 divisors, whose sum is σ = 661521564. Its totient is φ = 661521562.

The previous prime is 661521551. The next prime is 661521577. The reversal of 661521563 is 365125166.

661521563 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661521563 - 2¹⁶ = 661456027 is a prime.

It is a super-2 number, since 2×661521563² = 875221556627925938, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (661521463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330760781 + 330760782.

It is an arithmetic number, because the mean of its divisors is an integer number (330760782).

Almost surely, 2^661521563 is an apocalyptic number.

661521563 is a deficient number, since it is larger than the sum of its proper divisors (1).

661521563 is an equidigital number, since it uses as much as digits as its factorization.

661521563 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32400, while the sum is 35.

The square root of 661521563 is about 25720.0614890400. The cubic root of 661521563 is about 871.3273274182.

The spelling of 661521563 in words is "six hundred sixty-one million, five hundred twenty-one thousand, five hundred sixty-three".