20509725 has 24 divisors (see below), whose sum is σ = 34472992. Its totient is φ = 10756800.

The previous prime is 20509679. The next prime is 20509733. The reversal of 20509725 is 52790502.

20509725 = 348² + 349² + ... + 469².

It is a happy number.

It is not a de Polignac number, because 20509725 - 2⁶ = 20509661 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20509692 and 20509701.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 2334 + ... + 6816.

Almost surely, 2^20509725 is an apocalyptic number.

20509725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

20509725 is a deficient number, since it is larger than the sum of its proper divisors (13963267).

20509725 is a wasteful number, since it uses less digits than its factorization.

20509725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4557 (or 4552 counting only the distinct ones).

The product of its (nonzero) digits is 6300, while the sum is 30.

The square root of 20509725 is about 4528.7663883225. The cubic root of 20509725 is about 273.7284547585.

The spelling of 20509725 in words is "twenty million, five hundred nine thousand, seven hundred twenty-five".