20001551 has 2 divisors, whose sum is σ = 20001552. Its totient is φ = 20001550.

The previous prime is 20001521. The next prime is 20001557. The reversal of 20001551 is 15510002.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20001551 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20001557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10000775 + 10000776.

It is an arithmetic number, because the mean of its divisors is an integer number (10000776).

Almost surely, 2^20001551 is an apocalyptic number.

20001551 is a deficient number, since it is larger than the sum of its proper divisors (1).

20001551 is an equidigital number, since it uses as much as digits as its factorization.

20001551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 50, while the sum is 14.

The square root of 20001551 is about 4472.3093587094. The cubic root of 20001551 is about 271.4487782477.

Adding to 20001551 its reverse (15510002), we get a palindrome (35511553).

The spelling of 20001551 in words is "twenty million, one thousand, five hundred fifty-one".