20721025 has 24 divisors (see below), whose sum is σ = 27984320. Its totient is φ = 15128640.

The previous prime is 20721013. The next prime is 20721037. The reversal of 20721025 is 52012702.

It is an interprime number because it is at equal distance from previous prime (20721013) and next prime (20721037).

It is not a de Polignac number, because 20721025 - 2¹¹ = 20718977 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20720993 and 20721011.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33166 + ... + 33784.

Almost surely, 2^20721025 is an apocalyptic number.

20721025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

20721025 is a deficient number, since it is larger than the sum of its proper divisors (7263295).

20721025 is a wasteful number, since it uses less digits than its factorization.

20721025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 745 (or 740 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 20721025 is about 4552.0352590902. The cubic root of 20721025 is about 274.6652676574.

Adding to 20721025 its reverse (52012702), we get a palindrome (72733727).

The spelling of 20721025 in words is "twenty million, seven hundred twenty-one thousand, twenty-five".