21231507 has 24 divisors (see below), whose sum is σ = 32481792. Its totient is φ = 12303280.

The previous prime is 21231503. The next prime is 21231523. The reversal of 21231507 is 70513212.

It is not a de Polignac number, because 21231507 - 2² = 21231503 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21231503) 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, 7078 + ... + 9620.

It is an arithmetic number, because the mean of its divisors is an integer number (1353408).

Almost surely, 2^21231507 is an apocalyptic number.

21231507 is a deficient number, since it is larger than the sum of its proper divisors (11250285).

21231507 is a wasteful number, since it uses less digits than its factorization.

21231507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2591 (or 2580 counting only the distinct ones).

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

The square root of 21231507 is about 4607.7659445766. The cubic root of 21231507 is about 276.9025405770.

Adding to 21231507 its reverse (70513212), we get a palindrome (91744719).

The spelling of 21231507 in words is "twenty-one million, two hundred thirty-one thousand, five hundred seven".