21417720 has 32 divisors (see below), whose sum is σ = 64253520. Its totient is φ = 5711360.

The previous prime is 21417719. The next prime is 21417727. The reversal of 21417720 is 2771412.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21417727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 89121 + ... + 89360.

Almost surely, 2^21417720 is an apocalyptic number.

21417720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21417720 is an abundant number, since it is smaller than the sum of its proper divisors (42835800).

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

21417720 is a wasteful number, since it uses less digits than its factorization.

21417720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178495 (or 178491 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 24.

The square root of 21417720 is about 4627.9282621925. The cubic root of 21417720 is about 277.7097189113.

The spelling of 21417720 in words is "twenty-one million, four hundred seventeen thousand, seven hundred twenty".