21031867 has 4 divisors (see below), whose sum is σ = 21946320. Its totient is φ = 20117416.

The previous prime is 21031853. The next prime is 21031883. The reversal of 21031867 is 76813012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21031867 - 2⁷ = 21031739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21031807) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 457192 + ... + 457237.

It is an arithmetic number, because the mean of its divisors is an integer number (5486580).

Almost surely, 2^21031867 is an apocalyptic number.

21031867 is a deficient number, since it is larger than the sum of its proper divisors (914453).

21031867 is an equidigital number, since it uses as much as digits as its factorization.

21031867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 914452.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21031867 is about 4586.0513516532. The cubic root of 21031867 is about 276.0319004995.

Adding to 21031867 its reverse (76813012), we get a palindrome (97844879).

The spelling of 21031867 in words is "twenty-one million, thirty-one thousand, eight hundred sixty-seven".