21194721 has 6 divisors (see below), whose sum is σ = 30614610. Its totient is φ = 14129808.

The previous prime is 21194689. The next prime is 21194773. The reversal of 21194721 is 12749112.

It can be written as a sum of positive squares in only one way, i.e., 13242321 + 7952400 = 3639^2 + 2820^2 .

It is not a de Polignac number, because 21194721 - 2⁵ = 21194689 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21194021) 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 5 ways as a sum of consecutive naturals, for example, 1177476 + ... + 1177493.

It is an arithmetic number, because the mean of its divisors is an integer number (5102435).

Almost surely, 2^21194721 is an apocalyptic number.

It is an amenable number.

21194721 is a deficient number, since it is larger than the sum of its proper divisors (9419889).

21194721 is a wasteful number, since it uses less digits than its factorization.

21194721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2354975 (or 2354972 counting only the distinct ones).

The product of its digits is 1008, while the sum is 27.

The square root of 21194721 is about 4603.7724748297. The cubic root of 21194721 is about 276.7425264150.

The spelling of 21194721 in words is "twenty-one million, one hundred ninety-four thousand, seven hundred twenty-one".