21981907 has 4 divisors (see below), whose sum is σ = 22103536. Its totient is φ = 21860280.

The previous prime is 21981893. The next prime is 21981923. The reversal of 21981907 is 70918912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21981907 - 2¹⁵ = 21949139 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21981977) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60543 + ... + 60904.

It is an arithmetic number, because the mean of its divisors is an integer number (5525884).

Almost surely, 2^21981907 is an apocalyptic number.

21981907 is a deficient number, since it is larger than the sum of its proper divisors (121629).

21981907 is a wasteful number, since it uses less digits than its factorization.

21981907 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121628.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21981907 is about 4688.4866428305. The cubic root of 21981907 is about 280.1270979111.

The spelling of 21981907 in words is "twenty-one million, nine hundred eighty-one thousand, nine hundred seven".