21004997 has 8 divisors (see below), whose sum is σ = 23173080. Its totient is φ = 18915840.

The previous prime is 21004981. The next prime is 21004999. The reversal of 21004997 is 79940012.

It can be written as a sum of positive squares in 4 ways, for example, as 83521 + 20921476 = 289^2 + 4574^2 .

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 21004997 - 2⁴ = 21004981 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004999) 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, 19172 + ... + 20237.

It is an arithmetic number, because the mean of its divisors is an integer number (2896635).

Almost surely, 2^21004997 is an apocalyptic number.

It is an amenable number.

21004997 is a deficient number, since it is larger than the sum of its proper divisors (2168083).

21004997 is a wasteful number, since it uses less digits than its factorization.

21004997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39463.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 21004997 is about 4583.1208799245. The cubic root of 21004997 is about 275.9142989885.

The spelling of 21004997 in words is "twenty-one million, four thousand, nine hundred ninety-seven".