21101031 has 24 divisors (see below), whose sum is σ = 34978944. Its totient is φ = 12007440.

The previous prime is 21101027. The next prime is 21101033. The reversal of 21101031 is 13010112.

It is not a de Polignac number, because 21101031 - 2² = 21101027 is a prime.

It is a super-2 number, since 2×21101031² = 890507018525922, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101033) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18796 + ... + 19886.

It is an arithmetic number, because the mean of its divisors is an integer number (1457456).

Almost surely, 2^21101031 is an apocalyptic number.

21101031 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21101031 is a deficient number, since it is larger than the sum of its proper divisors (13877913).

21101031 is a wasteful number, since it uses less digits than its factorization.

21101031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1411 (or 1408 counting only the distinct ones).

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

The square root of 21101031 is about 4593.5858542102. The cubic root of 21101031 is about 276.3341494768.

Adding to 21101031 its reverse (13010112), we get a palindrome (34111143).

The spelling of 21101031 in words is "twenty-one million, one hundred one thousand, thirty-one".