21715740 has 72 divisors (see below), whose sum is σ = 66288768. Its totient is φ = 5754240.

The previous prime is 21715723. The next prime is 21715741. The reversal of 21715740 is 4751712.

21715740 is a `hidden beast` number, since 21 + 71 + 574 + 0 = 666.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21715741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39870 + ... + 40410.

Almost surely, 2^21715740 is an apocalyptic number.

21715740 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 21715740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33144384).

21715740 is an abundant number, since it is smaller than the sum of its proper divisors (44573028).

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

21715740 is a wasteful number, since it uses less digits than its factorization.

21715740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 779 (or 774 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21715740 is about 4660.0150214350. The cubic root of 21715740 is about 278.9918678017.

The spelling of 21715740 in words is "twenty-one million, seven hundred fifteen thousand, seven hundred forty".