21243490 has 16 divisors (see below), whose sum is σ = 39901248. Its totient is φ = 8127856.

The previous prime is 21243473. The next prime is 21243503. The reversal of 21243490 is 9434212.

21243490 = T₁₆₄ + T₁₆₅ + ... + T₅₀₈.

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, 45952 + ... + 46411.

It is an arithmetic number, because the mean of its divisors is an integer number (2493828).

Almost surely, 2^21243490 is an apocalyptic number.

21243490 is a deficient number, since it is larger than the sum of its proper divisors (18657758).

21243490 is a wasteful number, since it uses less digits than its factorization.

21243490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92393.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 21243490 is about 4609.0660659183. The cubic root of 21243490 is about 276.9546251055.

The spelling of 21243490 in words is "twenty-one million, two hundred forty-three thousand, four hundred ninety".