21191973 has 32 divisors (see below), whose sum is σ = 32962560. Its totient is φ = 11975040.

The previous prime is 21191969. The next prime is 21191977. The reversal of 21191973 is 37919112.

It is an interprime number because it is at equal distance from previous prime (21191969) and next prime (21191977).

It is not a de Polignac number, because 21191973 - 2² = 21191969 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21191977) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 45540 + ... + 46002.

It is an arithmetic number, because the mean of its divisors is an integer number (1030080).

Almost surely, 2^21191973 is an apocalyptic number.

It is an amenable number.

21191973 is a deficient number, since it is larger than the sum of its proper divisors (11770587).

21191973 is a wasteful number, since it uses less digits than its factorization.

21191973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 569.

The product of its digits is 3402, while the sum is 33.

The square root of 21191973 is about 4603.4740142636. The cubic root of 21191973 is about 276.7305655540.

The spelling of 21191973 in words is "twenty-one million, one hundred ninety-one thousand, nine hundred seventy-three".