21031011 has 12 divisors (see below), whose sum is σ = 30427488. Its totient is φ = 13997904.

The previous prime is 21031009. The next prime is 21031019. The reversal of 21031011 is 11013012.

It is not a de Polignac number, because 21031011 - 2¹ = 21031009 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21030984 and 21031002.

It is not an unprimeable number, because it can be changed into a prime (21031019) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5446 + ... + 8468.

It is an arithmetic number, because the mean of its divisors is an integer number (2535624).

Almost surely, 2^21031011 is an apocalyptic number.

21031011 is a deficient number, since it is larger than the sum of its proper divisors (9396477).

21031011 is a wasteful number, since it uses less digits than its factorization.

21031011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3802 (or 3799 counting only the distinct ones).

The product of its (nonzero) digits is 6, while the sum is 9.

The square root of 21031011 is about 4585.9580242301. The cubic root of 21031011 is about 276.0281556028.

Adding to 21031011 its reverse (11013012), we get a palindrome (32044023).

The spelling of 21031011 in words is "twenty-one million, thirty-one thousand, eleven".