21051090 has 48 divisors (see below), whose sum is σ = 56766528. Its totient is φ = 5612976.

The previous prime is 21051059. The next prime is 21051091. The reversal of 21051090 is 9015012.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21051091) 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 23 ways as a sum of consecutive naturals, for example, 1902 + ... + 6761.

It is an arithmetic number, because the mean of its divisors is an integer number (1182636).

Almost surely, 2^21051090 is an apocalyptic number.

21051090 is an abundant number, since it is smaller than the sum of its proper divisors (35715438).

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

21051090 is an equidigital number, since it uses as much as digits as its factorization.

21051090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8685 (or 8673 counting only the distinct ones).

The product of its (nonzero) digits is 90, while the sum is 18.

The square root of 21051090 is about 4588.1466846647. The cubic root of 21051090 is about 276.1159720570.

The spelling of 21051090 in words is "twenty-one million, fifty-one thousand, ninety".