21273390 has 96 divisors (see below), whose sum is σ = 59304960. Its totient is φ = 5277888.

The previous prime is 21273359. The next prime is 21273391. The reversal of 21273390 is 9337212.

21273390 = T₃₃₃ + T₃₃₄ + ... + T₅₄₇.

21273390 is a `hidden beast` number, since 2 + 1 + 273 + 390 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21273391) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 88891 + ... + 89129.

It is an arithmetic number, because the mean of its divisors is an integer number (617760).

Almost surely, 2^21273390 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21273390, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29652480).

21273390 is an abundant number, since it is smaller than the sum of its proper divisors (38031570).

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

21273390 is a wasteful number, since it uses less digits than its factorization.

21273390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318 (or 315 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 21273390 is about 4612.3085326114. The cubic root of 21273390 is about 277.0845011477.

The spelling of 21273390 in words is "twenty-one million, two hundred seventy-three thousand, three hundred ninety".