21245831 has 4 divisors (see below), whose sum is σ = 21764064. Its totient is φ = 20727600.

The previous prime is 21245803. The next prime is 21245839. The reversal of 21245831 is 13854212.

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 21245831 - 2¹⁰ = 21244807 is a prime.

It is a super-2 number, since 2×21245831² = 902770669761122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21245831.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21245839) 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, 259055 + ... + 259136.

It is an arithmetic number, because the mean of its divisors is an integer number (5441016).

Almost surely, 2^21245831 is an apocalyptic number.

21245831 is a deficient number, since it is larger than the sum of its proper divisors (518233).

21245831 is an equidigital number, since it uses as much as digits as its factorization.

21245831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 518232.

The product of its digits is 1920, while the sum is 26.

The square root of 21245831 is about 4609.3200149263. The cubic root of 21245831 is about 276.9647980567.

The spelling of 21245831 in words is "twenty-one million, two hundred forty-five thousand, eight hundred thirty-one".