21331390 has 16 divisors (see below), whose sum is σ = 38452320. Its totient is φ = 8520160.

The previous prime is 21331369. The next prime is 21331399. The reversal of 21331390 is 9313312.

21331390 is nontrivially palindromic in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331399) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9276 + ... + 11344.

It is an arithmetic number, because the mean of its divisors is an integer number (2403270).

Almost surely, 2^21331390 is an apocalyptic number.

21331390 is a deficient number, since it is larger than the sum of its proper divisors (17120930).

21331390 is a wasteful number, since it uses less digits than its factorization.

21331390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3107.

The product of its (nonzero) digits is 486, while the sum is 22.

The square root of 21331390 is about 4618.5917767216. The cubic root of 21331390 is about 277.3360880340.

The spelling of 21331390 in words is "twenty-one million, three hundred thirty-one thousand, three hundred ninety".