21007897 has 8 divisors (see below), whose sum is σ = 21777800. Its totient is φ = 20248704.

The previous prime is 21007891. The next prime is 21007913. The reversal of 21007897 is 79870012.

It can be written as a sum of positive squares in 4 ways, for example, as 15713296 + 5294601 = 3964^2 + 2301^2 .

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-21007897 is a prime.

It is a Duffinian number.

It is a zygodrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21007891) 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, 1429 + ... + 6637.

It is an arithmetic number, because the mean of its divisors is an integer number (2722225).

Almost surely, 2^21007897 is an apocalyptic number.

It is an amenable number.

21007897 is a deficient number, since it is larger than the sum of its proper divisors (769903).

21007897 is a wasteful number, since it uses less digits than its factorization.

21007897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5355.

The product of its (nonzero) digits is 7056, while the sum is 34.

The square root of 21007897 is about 4583.4372473069. The cubic root of 21007897 is about 275.9269961997.

It can be divided in two parts, 21007 and 897, that added together give a square (21904 = 148²).

The spelling of 21007897 in words is "twenty-one million, seven thousand, eight hundred ninety-seven".