21505746 has 16 divisors (see below), whose sum is σ = 43341408. Its totient is φ = 7113600.

The previous prime is 21505721. The next prime is 21505751. The reversal of 21505746 is 64750512.

It is a super-2 number, since 2×21505746² = 924994222033032, which contains 22 as substring.

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, 12895 + ... + 14466.

It is an arithmetic number, because the mean of its divisors is an integer number (2708838).

Almost surely, 2^21505746 is an apocalyptic number.

21505746 is an abundant number, since it is smaller than the sum of its proper divisors (21835662).

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

21505746 is a wasteful number, since it uses less digits than its factorization.

21505746 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27497.

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 21505746 is about 4637.4288134698. The cubic root of 21505746 is about 278.0896576056.

The spelling of 21505746 in words is "twenty-one million, five hundred five thousand, seven hundred forty-six".