21291946 has 16 divisors (see below), whose sum is σ = 35325864. Its totient is φ = 9561024.

The previous prime is 21291943. The next prime is 21291961. The reversal of 21291946 is 64919212.

It can be written as a sum of positive squares in 4 ways, for example, as 18533025 + 2758921 = 4305^2 + 1661^2 .

It is not an unprimeable number, because it can be changed into a prime (21291943) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10105 + ... + 12028.

Almost surely, 2^21291946 is an apocalyptic number.

21291946 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21291946 is a deficient number, since it is larger than the sum of its proper divisors (14033918).

21291946 is a wasteful number, since it uses less digits than its factorization.

21291946 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22185.

The product of its digits is 7776, while the sum is 34.

The square root of 21291946 is about 4614.3196681634. The cubic root of 21291946 is about 277.1650412934.

The spelling of 21291946 in words is "twenty-one million, two hundred ninety-one thousand, nine hundred forty-six".