21900390 has 32 divisors (see below), whose sum is σ = 52704000. Its totient is φ = 5824224.

The previous prime is 21900379. The next prime is 21900391. The reversal of 21900390 is 9300912.

21900390 = T₉₆₄ + T₉₆₅ + ... + T₁₀₀₈.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21900390.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21900391) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13861 + ... + 15359.

It is an arithmetic number, because the mean of its divisors is an integer number (1647000).

Almost surely, 2^21900390 is an apocalyptic number.

21900390 is an abundant number, since it is smaller than the sum of its proper divisors (30803610).

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

21900390 is a wasteful number, since it uses less digits than its factorization.

21900390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1996.

The product of its (nonzero) digits is 486, while the sum is 24.

The square root of 21900390 is about 4679.7852514832. The cubic root of 21900390 is about 279.7803975399.

The spelling of 21900390 in words is "twenty-one million, nine hundred thousand, three hundred ninety".