21431390 has 16 divisors (see below), whose sum is σ = 40846032. Its totient is φ = 8068224.

The previous prime is 21431387. The next prime is 21431401. The reversal of 21431390 is 9313412.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 62864 + ... + 63203.

It is an arithmetic number, because the mean of its divisors is an integer number (2552877).

Almost surely, 2^21431390 is an apocalyptic number.

21431390 is a deficient number, since it is larger than the sum of its proper divisors (19414642).

21431390 is a wasteful number, since it uses less digits than its factorization.

21431390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126091.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 21431390 is about 4629.4049293619. The cubic root of 21431390 is about 277.7687896944.

The spelling of 21431390 in words is "twenty-one million, four hundred thirty-one thousand, three hundred ninety".