20721475 has 6 divisors (see below), whose sum is σ = 25694660. Its totient is φ = 16577160.

The previous prime is 20721461. The next prime is 20721479. The reversal of 20721475 is 57412702.

It is not a de Polignac number, because 20721475 - 2²¹ = 18624323 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20721479) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 414405 + ... + 414454.

Almost surely, 2^20721475 is an apocalyptic number.

20721475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

20721475 is a deficient number, since it is larger than the sum of its proper divisors (4973185).

20721475 is an equidigital number, since it uses as much as digits as its factorization.

20721475 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 828869 (or 828864 counting only the distinct ones).

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 20721475 is about 4552.0846872614. The cubic root of 20721475 is about 274.6672559515.

The spelling of 20721475 in words is "twenty million, seven hundred twenty-one thousand, four hundred seventy-five".