20513551 has 2 divisors, whose sum is σ = 20513552. Its totient is φ = 20513550.

The previous prime is 20513531. The next prime is 20513557. The reversal of 20513551 is 15531502.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20513551 - 2⁹ = 20513039 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20513557) by changing a digit.

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 as a sum of consecutive naturals, namely, 10256775 + 10256776.

It is an arithmetic number, because the mean of its divisors is an integer number (10256776).

Almost surely, 2^20513551 is an apocalyptic number.

20513551 is a deficient number, since it is larger than the sum of its proper divisors (1).

20513551 is an equidigital number, since it uses as much as digits as its factorization.

20513551 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 750, while the sum is 22.

The square root of 20513551 is about 4529.1887794615. The cubic root of 20513551 is about 273.7454746512.

The spelling of 20513551 in words is "twenty million, five hundred thirteen thousand, five hundred fifty-one".