21741720 has 256 divisors, whose sum is σ = 88058880. Its totient is φ = 4147200.

The previous prime is 21741689. The next prime is 21741743. The reversal of 21741720 is 2714712.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 120030 + ... + 120210.

It is an arithmetic number, because the mean of its divisors is an integer number (343980).

Almost surely, 2^21741720 is an apocalyptic number.

21741720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21741720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44029440).

21741720 is an abundant number, since it is smaller than the sum of its proper divisors (66317160).

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

21741720 is a wasteful number, since it uses less digits than its factorization.

21741720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226 (or 222 counting only the distinct ones).

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

The square root of 21741720 is about 4662.8017328641. The cubic root of 21741720 is about 279.1030823729.

The spelling of 21741720 in words is "twenty-one million, seven hundred forty-one thousand, seven hundred twenty".