21420216 has 24 divisors (see below), whose sum is σ = 58013280. Its totient is φ = 7140048.

The previous prime is 21420209. The next prime is 21420227. The reversal of 21420216 is 61202412.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 148680 + ... + 148823.

It is an arithmetic number, because the mean of its divisors is an integer number (2417220).

Almost surely, 2^21420216 is an apocalyptic number.

It is an amenable number.

21420216 is an abundant number, since it is smaller than the sum of its proper divisors (36593064).

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

21420216 is a wasteful number, since it uses less digits than its factorization.

21420216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297515 (or 297508 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21420216 is about 4628.1979214377. The cubic root of 21420216 is about 277.7205064980.

Adding to 21420216 its reverse (61202412), we get a palindrome (82622628).

The spelling of 21420216 in words is "twenty-one million, four hundred twenty thousand, two hundred sixteen".