21240290 has 16 divisors (see below), whose sum is σ = 40245120. Its totient is φ = 8048880.

The previous prime is 21240283. The next prime is 21240311. The reversal of 21240290 is 9204212.

It is a super-2 number, since 2×21240290² = 902299838568200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55706 + ... + 56085.

It is an arithmetic number, because the mean of its divisors is an integer number (2515320).

Almost surely, 2^21240290 is an apocalyptic number.

21240290 is a deficient number, since it is larger than the sum of its proper divisors (19004830).

21240290 is a wasteful number, since it uses less digits than its factorization.

21240290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111817.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21240290 is about 4608.7189109339. The cubic root of 21240290 is about 276.9407181109.

The spelling of 21240290 in words is "twenty-one million, two hundred forty thousand, two hundred ninety".