21445390 has 32 divisors (see below), whose sum is σ = 40287456. Its totient is φ = 8211840.

The previous prime is 21445387. The next prime is 21445393. The reversal of 21445390 is 9354412.

It is an interprime number because it is at equal distance from previous prime (21445387) and next prime (21445393).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21445393) by changing a digit.

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 in 15 ways as a sum of consecutive naturals, for example, 22320 + ... + 23260.

It is an arithmetic number, because the mean of its divisors is an integer number (1258983).

Almost surely, 2^21445390 is an apocalyptic number.

21445390 is a deficient number, since it is larger than the sum of its proper divisors (18842066).

21445390 is a wasteful number, since it uses less digits than its factorization.

21445390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1044.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21445390 is about 4630.9167558919. The cubic root of 21445390 is about 277.8292604429.

The spelling of 21445390 in words is "twenty-one million, four hundred forty-five thousand, three hundred ninety".