21650831 has 2 divisors, whose sum is σ = 21650832. Its totient is φ = 21650830.

The previous prime is 21650813. The next prime is 21650857. The reversal of 21650831 is 13805612.

Together with previous prime (21650813) it forms an Ormiston pair, because they use the same digits, order apart.

It is an a-pointer prime, because the next prime (21650857) can be obtained adding 21650831 to its sum of digits (26).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21650831 - 2¹⁴ = 21634447 is a prime.

It is a super-2 number, since 2×21650831² = 937516965981122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21650831.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21650131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825415 + 10825416.

It is an arithmetic number, because the mean of its divisors is an integer number (10825416).

Almost surely, 2^21650831 is an apocalyptic number.

21650831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21650831 is an equidigital number, since it uses as much as digits as its factorization.

21650831 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21650831 is about 4653.0453468669. The cubic root of 21650831 is about 278.7136186909.

The spelling of 21650831 in words is "twenty-one million, six hundred fifty thousand, eight hundred thirty-one".