21706740 has 144 divisors (see below), whose sum is σ = 75741120. Its totient is φ = 4976640.

The previous prime is 21706717. The next prime is 21706777. The reversal of 21706740 is 4760712.

It is a super-2 number, since 2×21706740² = 942365122855200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 37332 + ... + 37908.

It is an arithmetic number, because the mean of its divisors is an integer number (525980).

Almost surely, 2^21706740 is an apocalyptic number.

21706740 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 21706740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37870560).

21706740 is an abundant number, since it is smaller than the sum of its proper divisors (54034380).

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

21706740 is a wasteful number, since it uses less digits than its factorization.

21706740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 622 (or 617 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 27.

The square root of 21706740 is about 4659.0492592373. The cubic root of 21706740 is about 278.9533201281.

The spelling of 21706740 in words is "twenty-one million, seven hundred six thousand, seven hundred forty".