21199831 has 2 divisors, whose sum is σ = 21199832. Its totient is φ = 21199830.

The previous prime is 21199811. The next prime is 21199837. The reversal of 21199831 is 13899112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21199831 - 2²³ = 12811223 is a prime.

It is a super-2 number, since 2×21199831² = 898865668857122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21199837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10599915 + 10599916.

It is an arithmetic number, because the mean of its divisors is an integer number (10599916).

Almost surely, 2^21199831 is an apocalyptic number.

21199831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21199831 is an equidigital number, since it uses as much as digits as its factorization.

21199831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 34.

The square root of 21199831 is about 4604.3274210247. The cubic root of 21199831 is about 276.7647652966.

The spelling of 21199831 in words is "twenty-one million, one hundred ninety-nine thousand, eight hundred thirty-one".