21521416 has 32 divisors (see below), whose sum is σ = 46347840. Its totient is φ = 9177408.

The previous prime is 21521413. The next prime is 21521419. The reversal of 21521416 is 61412512.

It is an interprime number because it is at equal distance from previous prime (21521413) and next prime (21521419).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521413) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11866 + ... + 13558.

It is an arithmetic number, because the mean of its divisors is an integer number (1448370).

Almost surely, 2^21521416 is an apocalyptic number.

It is an amenable number.

21521416 is an abundant number, since it is smaller than the sum of its proper divisors (24826424).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21521416 is a wasteful number, since it uses less digits than its factorization.

21521416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1933 (or 1929 counting only the distinct ones).

The product of its digits is 480, while the sum is 22.

The square root of 21521416 is about 4639.1180196240. The cubic root of 21521416 is about 278.1571838530.

Adding to 21521416 its reverse (61412512), we get a palindrome (82933928).

The spelling of 21521416 in words is "twenty-one million, five hundred twenty-one thousand, four hundred sixteen".