20721115 has 8 divisors (see below), whose sum is σ = 26174160. Its totient is φ = 15704352.

The previous prime is 20721101. The next prime is 20721131. The reversal of 20721115 is 51112702.

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 20721115 - 2⁵ = 20721083 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a junction number, because it is equal to n+sod(n) for n = 20721092 and 20721101.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 108964 + ... + 109153.

It is an arithmetic number, because the mean of its divisors is an integer number (3271770).

Almost surely, 2^20721115 is an apocalyptic number.

20721115 is a deficient number, since it is larger than the sum of its proper divisors (5453045).

20721115 is a wasteful number, since it uses less digits than its factorization.

20721115 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218141.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 20721115 is about 4552.0451447673. The cubic root of 20721115 is about 274.6656653185.

Adding to 20721115 its reverse (51112702), we get a palindrome (71833817).

The spelling of 20721115 in words is "twenty million, seven hundred twenty-one thousand, one hundred fifteen".