21990308 has 6 divisors (see below), whose sum is σ = 38483046. Its totient is φ = 10995152.

The previous prime is 21990259. The next prime is 21990337. The reversal of 21990308 is 80309912.

It can be written as a sum of positive squares in only one way, i.e., 11505664 + 10484644 = 3392^2 + 3238^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2748785 + ... + 2748792.

It is an arithmetic number, because the mean of its divisors is an integer number (6413841).

Almost surely, 2^21990308 is an apocalyptic number.

It is an amenable number.

21990308 is a deficient number, since it is larger than the sum of its proper divisors (16492738).

21990308 is a wasteful number, since it uses less digits than its factorization.

21990308 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5497581 (or 5497579 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 21990308 is about 4689.3824753372. The cubic root of 21990308 is about 280.1627794986.

The spelling of 21990308 in words is "twenty-one million, nine hundred ninety thousand, three hundred eight".