21740981 has 8 divisors (see below), whose sum is σ = 22809600. Its totient is φ = 20693680.

The previous prime is 21740963. The next prime is 21740987. The reversal of 21740981 is 18904712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21740981 is a prime.

It is a super-2 number, since 2×21740981² = 945340509684722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21740987) 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, 3221 + ... + 7338.

It is an arithmetic number, because the mean of its divisors is an integer number (2851200).

Almost surely, 2^21740981 is an apocalyptic number.

It is an amenable number.

21740981 is a deficient number, since it is larger than the sum of its proper divisors (1068619).

21740981 is a wasteful number, since it uses less digits than its factorization.

21740981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10659.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21740981 is about 4662.7224879892. The cubic root of 21740981 is about 279.0999201037.

The spelling of 21740981 in words is "twenty-one million, seven hundred forty thousand, nine hundred eighty-one".