21277831 has 2 divisors, whose sum is σ = 21277832. Its totient is φ = 21277830.

The previous prime is 21277813. The next prime is 21277871. The reversal of 21277831 is 13877212.

Together with previous prime (21277813) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21277831 - 2¹³ = 21269639 is a prime.

It is a super-2 number, since 2×21277831² = 905492184129122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21277793 and 21277802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21277871) 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 as a sum of consecutive naturals, namely, 10638915 + 10638916.

It is an arithmetic number, because the mean of its divisors is an integer number (10638916).

Almost surely, 2^21277831 is an apocalyptic number.

21277831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21277831 is an equidigital number, since it uses as much as digits as its factorization.

21277831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4704, while the sum is 31.

The square root of 21277831 is about 4612.7899366869. The cubic root of 21277831 is about 277.1037810502.

The spelling of 21277831 in words is "twenty-one million, two hundred seventy-seven thousand, eight hundred thirty-one".