21420590 has 16 divisors (see below), whose sum is σ = 40233888. Its totient is φ = 8195616.

The previous prime is 21420587. The next prime is 21420643. The reversal of 21420590 is 9502412.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 46337 + ... + 46796.

It is an arithmetic number, because the mean of its divisors is an integer number (2514618).

Almost surely, 2^21420590 is an apocalyptic number.

21420590 is a deficient number, since it is larger than the sum of its proper divisors (18813298).

21420590 is a wasteful number, since it uses less digits than its factorization.

21420590 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93163.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21420590 is about 4628.2383257564. The cubic root of 21420590 is about 277.7221228350.

The spelling of 21420590 in words is "twenty-one million, four hundred twenty thousand, five hundred ninety".