999997521 has 16 divisors (see below), whose sum is σ = 1364588544. Its totient is φ = 651096144.

The previous prime is 999997489. The next prime is 999997543. The reversal of 999997521 is 125799999.

It is not a de Polignac number, because 999997521 - 2⁵ = 999997489 is a prime.

It is a super-2 number, since 2×999997521² = 1999990084012290882, which contains 22 as substring.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (999997561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 61386 + ... + 75948.

It is an arithmetic number, because the mean of its divisors is an integer number (85286784).

Almost surely, 2^999997521 is an apocalyptic number.

It is an amenable number.

999997521 is a deficient number, since it is larger than the sum of its proper divisors (364591023).

999997521 is a wasteful number, since it uses less digits than its factorization.

999997521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15100.

The product of its digits is 4133430, while the sum is 60.

The square root of 999997521 is about 31622.7374052279. The cubic root of 999997521 is about 999.9991736660. Note that the first 3 decimals are identical.

The spelling of 999997521 in words is "nine hundred ninety-nine million, nine hundred ninety-seven thousand, five hundred twenty-one".