21981265 has 8 divisors (see below), whose sum is σ = 26402688. Its totient is φ = 17568240.

The previous prime is 21981251. The next prime is 21981283. The reversal of 21981265 is 56218912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21981265 - 2⁷ = 21981137 is a prime.

It is a super-2 number, since 2×21981265² = 966352022000450, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21981265.

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, 9250 + ... + 11380.

It is an arithmetic number, because the mean of its divisors is an integer number (3300336).

Almost surely, 2^21981265 is an apocalyptic number.

It is an amenable number.

21981265 is a deficient number, since it is larger than the sum of its proper divisors (4421423).

21981265 is a wasteful number, since it uses less digits than its factorization.

21981265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4199.

The product of its digits is 8640, while the sum is 34.

The square root of 21981265 is about 4688.4181767415. The cubic root of 21981265 is about 280.1243707691.

The spelling of 21981265 in words is "twenty-one million, nine hundred eighty-one thousand, two hundred sixty-five".