781998421 has 2 divisors, whose sum is σ = 781998422. Its totient is φ = 781998420.

The previous prime is 781998397. The next prime is 781998439. The reversal of 781998421 is 124899187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 682776900 + 99221521 = 26130^2 + 9961^2 .

It is a cyclic number.

It is not a de Polignac number, because 781998421 - 2¹³ = 781990229 is a prime.

It is a super-2 number, since 2×781998421² = 1223043060892986482, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781998461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390999210 + 390999211.

It is an arithmetic number, because the mean of its divisors is an integer number (390999211).

Almost surely, 2^781998421 is an apocalyptic number.

It is an amenable number.

781998421 is a deficient number, since it is larger than the sum of its proper divisors (1).

781998421 is an equidigital number, since it uses as much as digits as its factorization.

781998421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 290304, while the sum is 49.

The square root of 781998421 is about 27964.2346757425. The cubic root of 781998421 is about 921.3018828263.

The spelling of 781998421 in words is "seven hundred eighty-one million, nine hundred ninety-eight thousand, four hundred twenty-one".