21670031 has 2 divisors, whose sum is σ = 21670032. Its totient is φ = 21670030.

The previous prime is 21670009. The next prime is 21670037. The reversal of 21670031 is 13007612.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21670031 - 2¹⁰ = 21669007 is a prime.

It is a super-2 number, since 2×21670031² = 939180487081922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21669985 and 21670012.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21670037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10835015 + 10835016.

It is an arithmetic number, because the mean of its divisors is an integer number (10835016).

Almost surely, 2^21670031 is an apocalyptic number.

21670031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21670031 is an equidigital number, since it uses as much as digits as its factorization.

21670031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 252, while the sum is 20.

The square root of 21670031 is about 4655.1080545998. The cubic root of 21670031 is about 278.7959822795.

Adding to 21670031 its reverse (13007612), we get a palindrome (34677643).

The spelling of 21670031 in words is "twenty-one million, six hundred seventy thousand, thirty-one".