21437216 has 12 divisors (see below), whose sum is σ = 42204582. Its totient is φ = 10718592.

The previous prime is 21437201. The next prime is 21437231. The reversal of 21437216 is 61273412.

It is an interprime number because it is at equal distance from previous prime (21437201) and next prime (21437231).

It can be written as a sum of positive squares in only one way, i.e., 17673616 + 3763600 = 4204^2 + 1940^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334925 + ... + 334988.

Almost surely, 2^21437216 is an apocalyptic number.

It is an amenable number.

21437216 is a deficient number, since it is larger than the sum of its proper divisors (20767366).

21437216 is an equidigital number, since it uses as much as digits as its factorization.

21437216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 669923 (or 669915 counting only the distinct ones).

The product of its digits is 2016, while the sum is 26.

The square root of 21437216 is about 4630.0341251442. The cubic root of 21437216 is about 277.7939573628.

The spelling of 21437216 in words is "twenty-one million, four hundred thirty-seven thousand, two hundred sixteen".