21025831 has 2 divisors, whose sum is σ = 21025832. Its totient is φ = 21025830.

The previous prime is 21025819. The next prime is 21025861. The reversal of 21025831 is 13852012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21025831 - 2¹⁹ = 20501543 is a prime.

It is a super-2 number, since 2×21025831² = 884171138481122, which contains 22 as substring.

It is a Chen prime.

It is equal to p_1331509 and since 21025831 and 1331509 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21025811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10512915 + 10512916.

It is an arithmetic number, because the mean of its divisors is an integer number (10512916).

Almost surely, 2^21025831 is an apocalyptic number.

21025831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21025831 is an equidigital number, since it uses as much as digits as its factorization.

21025831 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21025831 is about 4585.3932219604. The cubic root of 21025831 is about 276.0054915592.

Adding to 21025831 its reverse (13852012), we get a palindrome (34877843).

The spelling of 21025831 in words is "twenty-one million, twenty-five thousand, eight hundred thirty-one".