21431516 has 6 divisors (see below), whose sum is σ = 37505160. Its totient is φ = 10715756.

The previous prime is 21431507. The next prime is 21431521. The reversal of 21431516 is 61513412.

It is a junction number, because it is equal to n+sod(n) for n = 21431491 and 21431500.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 2678936 + ... + 2678943.

It is an arithmetic number, because the mean of its divisors is an integer number (6250860).

Almost surely, 2^21431516 is an apocalyptic number.

It is an amenable number.

21431516 is a deficient number, since it is larger than the sum of its proper divisors (16073644).

21431516 is a wasteful number, since it uses less digits than its factorization.

21431516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5357883 (or 5357881 counting only the distinct ones).

The product of its digits is 720, while the sum is 23.

The square root of 21431516 is about 4629.4185380024. The cubic root of 21431516 is about 277.7693340485.

Adding to 21431516 its reverse (61513412), we get a palindrome (82944928).

The spelling of 21431516 in words is "twenty-one million, four hundred thirty-one thousand, five hundred sixteen".