21213507 has 8 divisors (see below), whose sum is σ = 32325376. Its totient is φ = 12121992.

The previous prime is 21213487. The next prime is 21213553. The reversal of 21213507 is 70531212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21213507 - 2⁸ = 21213251 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1010167 = 21213507 / (2 + 1 + 2 + 1 + 3 + 5 + 0 + 7).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21213407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 505063 + ... + 505104.

It is an arithmetic number, because the mean of its divisors is an integer number (4040672).

Almost surely, 2^21213507 is an apocalyptic number.

21213507 is a deficient number, since it is larger than the sum of its proper divisors (11111869).

21213507 is a wasteful number, since it uses less digits than its factorization.

21213507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1010177.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21213507 is about 4605.8123062061. The cubic root of 21213507 is about 276.8242661060.

Adding to 21213507 its reverse (70531212), we get a palindrome (91744719).

It can be divided in two parts, 2121 and 3507, that multiplied together give a palindrome (7438347).

The spelling of 21213507 in words is "twenty-one million, two hundred thirteen thousand, five hundred seven".