521619921 has 27 divisors (see below), whose sum is σ = 790020777. Its totient is φ = 331622280.

The previous prime is 521619907. The next prime is 521619929. The reversal of 521619921 is 129916125.

The square root of 521619921 is 22839.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 521619921 - 2¹⁹ = 521095633 is a prime.

It is not an unprimeable number, because it can be changed into a prime (521619929) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1575726 + ... + 1576056.

Almost surely, 2^521619921 is an apocalyptic number.

521619921 is the 22839-th square number.

521619921 is the 11420-th centered octagonal number.

It is an amenable number.

521619921 is a deficient number, since it is larger than the sum of its proper divisors (268400856).

521619921 is an equidigital number, since it uses as much as digits as its factorization.

521619921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 714 (or 357 counting only the distinct ones).

The product of its digits is 9720, while the sum is 36.

The cubic root of 521619921 is about 804.9793191966.

Multiplying 521619921 by its sum of digits (36), we get a square (18778317156 = 137034²).

The spelling of 521619921 in words is "five hundred twenty-one million, six hundred nineteen thousand, nine hundred twenty-one".