18969781 has 2 divisors, whose sum is σ = 18969782. Its totient is φ = 18969780.

The previous prime is 18969767. The next prime is 18969787. The reversal of 18969781 is 18796981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15132100 + 3837681 = 3890^2 + 1959^2 .

It is a cyclic number.

It is not a de Polignac number, because 18969781 - 2⁷ = 18969653 is a prime.

It is a super-2 number, since 2×18969781² = 719705182375922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18969787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9484890 + 9484891.

It is an arithmetic number, because the mean of its divisors is an integer number (9484891).

Almost surely, 2^18969781 is an apocalyptic number.

It is an amenable number.

18969781 is a deficient number, since it is larger than the sum of its proper divisors (1).

18969781 is an equidigital number, since it uses as much as digits as its factorization.

18969781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 217728, while the sum is 49.

The square root of 18969781 is about 4355.4312071252. The cubic root of 18969781 is about 266.6986223857.

The spelling of 18969781 in words is "eighteen million, nine hundred sixty-nine thousand, seven hundred eighty-one".