21961806 has 16 divisors (see below), whose sum is σ = 44668800. Its totient is φ = 7196408.

The previous prime is 21961801. The next prime is 21961813. The reversal of 21961806 is 60816912.

21961806 = T₃₀₈ + T₃₀₉ + ... + T₅₄₃.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21961801) by changing a digit.

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, 30666 + ... + 31373.

It is an arithmetic number, because the mean of its divisors is an integer number (2791800).

Almost surely, 2^21961806 is an apocalyptic number.

21961806 is an abundant number, since it is smaller than the sum of its proper divisors (22706994).

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

21961806 is a wasteful number, since it uses less digits than its factorization.

21961806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62103.

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21961806 is about 4686.3424970866. The cubic root of 21961806 is about 280.0416859704.

The spelling of 21961806 in words is "twenty-one million, nine hundred sixty-one thousand, eight hundred six".