21981012 has 12 divisors (see below), whose sum is σ = 51289056. Its totient is φ = 7327000.

The previous prime is 21980999. The next prime is 21981013. The reversal of 21981012 is 21018912.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981013) 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, 915864 + ... + 915887.

It is an arithmetic number, because the mean of its divisors is an integer number (4274088).

Almost surely, 2^21981012 is an apocalyptic number.

It is an amenable number.

21981012 is an abundant number, since it is smaller than the sum of its proper divisors (29308044).

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

21981012 is a wasteful number, since it uses less digits than its factorization.

21981012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1831758 (or 1831756 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 21981012 is about 4688.3911952822. The cubic root of 21981012 is about 280.1232960396.

Adding to 21981012 its reverse (21018912), we get a palindrome (42999924).

The spelling of 21981012 in words is "twenty-one million, nine hundred eighty-one thousand, twelve".