1554961781 has 2 divisors, whose sum is σ = 1554961782. Its totient is φ = 1554961780.

The previous prime is 1554961739. The next prime is 1554961783. The reversal of 1554961781 is 1871694551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 986902225 + 568059556 = 31415^2 + 23834^2 .

It is a cyclic number.

It is not a de Polignac number, because 1554961781 - 2⁶ = 1554961717 is a prime.

It is a super-2 number, since 2×1554961781² = 4835812280741383922, which contains 22 as substring.

Together with 1554961783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1554961783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 777480890 + 777480891.

It is an arithmetic number, because the mean of its divisors is an integer number (777480891).

Almost surely, 2^1554961781 is an apocalyptic number.

It is an amenable number.

1554961781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1554961781 is an equidigital number, since it uses as much as digits as its factorization.

1554961781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 302400, while the sum is 47.

The square root of 1554961781 is about 39433.0037024825. The cubic root of 1554961781 is about 1158.5281026636.

The spelling of 1554961781 in words is "one billion, five hundred fifty-four million, nine hundred sixty-one thousand, seven hundred eighty-one".