821784401 has 2 divisors, whose sum is σ = 821784402. Its totient is φ = 821784400.

The previous prime is 821784389. The next prime is 821784407. The reversal of 821784401 is 104487128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 772784401 + 49000000 = 27799^2 + 7000^2 .

It is a cyclic number.

It is not a de Polignac number, because 821784401 - 2²² = 817590097 is a prime.

It is not a weakly prime, because it can be changed into another prime (821784407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410892200 + 410892201.

It is an arithmetic number, because the mean of its divisors is an integer number (410892201).

Almost surely, 2^821784401 is an apocalyptic number.

It is an amenable number.

821784401 is a deficient number, since it is larger than the sum of its proper divisors (1).

821784401 is an equidigital number, since it uses as much as digits as its factorization.

821784401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14336, while the sum is 35.

The square root of 821784401 is about 28666.7821877517. The cubic root of 821784401 is about 936.6686061152.

The spelling of 821784401 in words is "eight hundred twenty-one million, seven hundred eighty-four thousand, four hundred one".