21120681 has 8 divisors (see below), whose sum is σ = 29817504. Its totient is φ = 13252160.

The previous prime is 21120677. The next prime is 21120689. The reversal of 21120681 is 18602112.

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

It is a cyclic number.

It is not a de Polignac number, because 21120681 - 2² = 21120677 is a prime.

It is a super-2 number, since 2×21120681² = 892166331807522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21120689) 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, 207015 + ... + 207116.

It is an arithmetic number, because the mean of its divisors is an integer number (3727188).

Almost surely, 2^21120681 is an apocalyptic number.

It is an amenable number.

21120681 is a deficient number, since it is larger than the sum of its proper divisors (8696823).

21120681 is a wasteful number, since it uses less digits than its factorization.

21120681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 414151.

The product of its (nonzero) digits is 192, while the sum is 21.

The square root of 21120681 is about 4595.7242084355. The cubic root of 21120681 is about 276.4199001270.

Adding to 21120681 its reverse (18602112), we get a palindrome (39722793).

Subtracting from 21120681 its reverse (18602112), we obtain a square (2518569 = 1587²).

The spelling of 21120681 in words is "twenty-one million, one hundred twenty thousand, six hundred eighty-one".