21749216 has 24 divisors (see below), whose sum is σ = 43069320. Its totient is φ = 10811008.

The previous prime is 21749213. The next prime is 21749219. The reversal of 21749216 is 61294712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21749213) and next prime (21749219).

It is a super-2 number, since 2×21749216² = 946056793229312, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21749213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3830 + ... + 7626.

It is an arithmetic number, because the mean of its divisors is an integer number (1794555).

Almost surely, 2^21749216 is an apocalyptic number.

It is an amenable number.

21749216 is a deficient number, since it is larger than the sum of its proper divisors (21320104).

21749216 is a wasteful number, since it uses less digits than its factorization.

21749216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3986 (or 3978 counting only the distinct ones).

The product of its digits is 6048, while the sum is 32.

The square root of 21749216 is about 4663.6054721642. The cubic root of 21749216 is about 279.1351546025.

The spelling of 21749216 in words is "twenty-one million, seven hundred forty-nine thousand, two hundred sixteen".