90021906 has 72 divisors (see below), whose sum is σ = 214024356. Its totient is φ = 27331200.

The previous prime is 90021881. The next prime is 90021907. The reversal of 90021906 is 60912009.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 60699681 + 29322225 = 7791^2 + 5415^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 90021906.

It is not an unprimeable number, because it can be changed into a prime (90021907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 307096 + ... + 307388.

Almost surely, 2^90021906 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 90021906, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107012178).

90021906 is an abundant number, since it is smaller than the sum of its proper divisors (124002450).

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

90021906 is a wasteful number, since it uses less digits than its factorization.

90021906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 428 (or 412 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 90021906 is about 9487.9874578332. The cubic root of 90021906 is about 448.1768308367.

The spelling of 90021906 in words is "ninety million, twenty-one thousand, nine hundred six".