821637990 has 48 divisors (see below), whose sum is σ = 2142790416. Its totient is φ = 218433600.

The previous prime is 821637989. The next prime is 821637997. The reversal of 821637990 is 99736128.

821637990 is a `hidden beast` number, since 8 + 2 + 1 + 637 + 9 + 9 + 0 = 666.

It is a super-2 number, since 2×821637990² = 1350177973222480200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821637997) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 16000 + ... + 43580.

It is an arithmetic number, because the mean of its divisors is an integer number (44641467).

Almost surely, 2^821637990 is an apocalyptic number.

821637990 is an abundant number, since it is smaller than the sum of its proper divisors (1321152426).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

821637990 is a wasteful number, since it uses less digits than its factorization.

821637990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27925 (or 27922 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The square root of 821637990 is about 28664.2284040579. The cubic root of 821637990 is about 936.6129764666.

The spelling of 821637990 in words is "eight hundred twenty-one million, six hundred thirty-seven thousand, nine hundred ninety".