20997231 has 4 divisors (see below), whose sum is σ = 27996312. Its totient is φ = 13998152.

The previous prime is 20997217. The next prime is 20997253. The reversal of 20997231 is 13279902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20997231 - 2⁷ = 20997103 is a prime.

It is a super-2 number, since 2×20997231² = 881767419334722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20997192 and 20997201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20997211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3499536 + ... + 3499541.

It is an arithmetic number, because the mean of its divisors is an integer number (6999078).

Almost surely, 2^20997231 is an apocalyptic number.

20997231 is a deficient number, since it is larger than the sum of its proper divisors (6999081).

20997231 is an equidigital number, since it uses as much as digits as its factorization.

20997231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6999080.

The product of its (nonzero) digits is 6804, while the sum is 33.

The square root of 20997231 is about 4582.2735623269. The cubic root of 20997231 is about 275.8802909765.

The spelling of 20997231 in words is "twenty million, nine hundred ninety-seven thousand, two hundred thirty-one".