21213031 has 12 divisors (see below), whose sum is σ = 25280640. Its totient is φ = 17737440.

The previous prime is 21213029. The next prime is 21213041. The reversal of 21213031 is 13031212.

It is not a de Polignac number, because 21213031 - 2¹ = 21213029 is a prime.

It is a super-2 number, since 2×21213031² = 899985368413922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213011) 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, 3271 + ... + 7288.

It is an arithmetic number, because the mean of its divisors is an integer number (2106720).

Almost surely, 2^21213031 is an apocalyptic number.

21213031 is a deficient number, since it is larger than the sum of its proper divisors (4067609).

21213031 is a wasteful number, since it uses less digits than its factorization.

21213031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10614 (or 10607 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21213031 is about 4605.7606320781. The cubic root of 21213031 is about 276.8221955803.

Adding to 21213031 its reverse (13031212), we get a palindrome (34244243).

The spelling of 21213031 in words is "twenty-one million, two hundred thirteen thousand, thirty-one".