21090638 has 8 divisors (see below), whose sum is σ = 31691088. Its totient is φ = 10526944.

The previous prime is 21090631. The next prime is 21090647. The reversal of 21090638 is 83609012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21090638² = 889630022494088, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21090638.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090631) 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 3 ways as a sum of consecutive naturals, for example, 7706 + ... + 10077.

It is an arithmetic number, because the mean of its divisors is an integer number (3961386).

Almost surely, 2^21090638 is an apocalyptic number.

21090638 is a deficient number, since it is larger than the sum of its proper divisors (10600450).

21090638 is a wasteful number, since it uses less digits than its factorization.

21090638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18378.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21090638 is about 4592.4544635739. The cubic root of 21090638 is about 276.2887739300.

The spelling of 21090638 in words is "twenty-one million, ninety thousand, six hundred thirty-eight".