821461781 has 16 divisors (see below), whose sum is σ = 948301824. Its totient is φ = 697019904.

The previous prime is 821461769. The next prime is 821461799. The reversal of 821461781 is 187164128.

It is a happy number.

It is not a de Polignac number, because 821461781 - 2⁶ = 821461717 is a prime.

It is a super-2 number, since 2×821461781² = 1349598915287383922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821460781) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 597611 + ... + 598983.

It is an arithmetic number, because the mean of its divisors is an integer number (59268864).

Almost surely, 2^821461781 is an apocalyptic number.

It is an amenable number.

821461781 is a deficient number, since it is larger than the sum of its proper divisors (126840043).

821461781 is a wasteful number, since it uses less digits than its factorization.

821461781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2180.

The product of its digits is 21504, while the sum is 38.

The square root of 821461781 is about 28661.1545650206. The cubic root of 821461781 is about 936.5460161436.

The spelling of 821461781 in words is "eight hundred twenty-one million, four hundred sixty-one thousand, seven hundred eighty-one".