620661521 has 4 divisors (see below), whose sum is σ = 620811444. Its totient is φ = 620511600.

The previous prime is 620661511. The next prime is 620661529. The reversal of 620661521 is 125166026.

620661521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 125166026 = 2 ⋅62583013.

It can be written as a sum of positive squares in 2 ways, for example, as 415140625 + 205520896 = 20375^2 + 14336^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-620661521 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (620661529) 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, 68570 + ... + 77091.

It is an arithmetic number, because the mean of its divisors is an integer number (155202861).

Almost surely, 2^620661521 is an apocalyptic number.

It is an amenable number.

620661521 is a deficient number, since it is larger than the sum of its proper divisors (149923).

620661521 is a wasteful number, since it uses less digits than its factorization.

620661521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149922.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 620661521 is about 24913.0793158935. The cubic root of 620661521 is about 853.0050594639.

The spelling of 620661521 in words is "six hundred twenty million, six hundred sixty-one thousand, five hundred twenty-one".