21531416 has 8 divisors (see below), whose sum is σ = 40371420. Its totient is φ = 10765704.

The previous prime is 21531379. The next prime is 21531439. The reversal of 21531416 is 61413512.

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 21531391 and 21531400.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1345706 + ... + 1345721.

Almost surely, 2^21531416 is an apocalyptic number.

It is an amenable number.

21531416 is a deficient number, since it is larger than the sum of its proper divisors (18840004).

21531416 is a wasteful number, since it uses less digits than its factorization.

21531416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2691433 (or 2691429 counting only the distinct ones).

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

The square root of 21531416 is about 4640.1956855288. The cubic root of 21531416 is about 278.2002594128.

Adding to 21531416 its reverse (61413512), we get a palindrome (82944928).

The spelling of 21531416 in words is "twenty-one million, five hundred thirty-one thousand, four hundred sixteen".