21531470 has 16 divisors (see below), whose sum is σ = 38813040. Its totient is φ = 8600064.

The previous prime is 21531443. The next prime is 21531479. The reversal of 21531470 is 7413512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531479) 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, 9134 + ... + 11246.

It is an arithmetic number, because the mean of its divisors is an integer number (2425815).

Almost surely, 2^21531470 is an apocalyptic number.

21531470 is a deficient number, since it is larger than the sum of its proper divisors (17281570).

21531470 is a wasteful number, since it uses less digits than its factorization.

21531470 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3139.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 21531470 is about 4640.2015042453. The cubic root of 21531470 is about 278.2004919846.

Adding to 21531470 its reverse (7413512), we get a palindrome (28944982).

The spelling of 21531470 in words is "twenty-one million, five hundred thirty-one thousand, four hundred seventy".