20505402551 has 2 divisors, whose sum is σ = 20505402552. Its totient is φ = 20505402550.

The previous prime is 20505402539. The next prime is 20505402557. The reversal of 20505402551 is 15520450502.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20505402551 - 2¹⁸ = 20505140407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20505402557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10252701275 + 10252701276.

It is an arithmetic number, because the mean of its divisors is an integer number (10252701276).

Almost surely, 2^20505402551 is an apocalyptic number.

20505402551 is a deficient number, since it is larger than the sum of its proper divisors (1).

20505402551 is an equidigital number, since it uses as much as digits as its factorization.

20505402551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10000, while the sum is 29.

The spelling of 20505402551 in words is "twenty billion, five hundred five million, four hundred two thousand, five hundred fifty-one".