21981545 has 16 divisors (see below), whose sum is σ = 26889408. Its totient is φ = 17248320.

The previous prime is 21981497. The next prime is 21981559. The reversal of 21981545 is 54518912.

It is not a de Polignac number, because 21981545 - 2²² = 17787241 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 96722 + ... + 96948.

It is an arithmetic number, because the mean of its divisors is an integer number (1680588).

Almost surely, 2^21981545 is an apocalyptic number.

It is an amenable number.

21981545 is a deficient number, since it is larger than the sum of its proper divisors (4907863).

21981545 is a wasteful number, since it uses less digits than its factorization.

21981545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520.

The product of its digits is 14400, while the sum is 35.

The square root of 21981545 is about 4688.4480374640. The cubic root of 21981545 is about 280.1255601833.

The spelling of 21981545 in words is "twenty-one million, nine hundred eighty-one thousand, five hundred forty-five".