21264981 has 8 divisors (see below), whose sum is σ = 28383744. Its totient is φ = 14161440.

The previous prime is 21264979. The next prime is 21265001. The reversal of 21264981 is 18946212.

21264981 is a nontrivial binomial coefficient, being equal to C(6522, 2).

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

It is not a de Polignac number, because 21264981 - 2¹ = 21264979 is a prime.

It is a super-2 number, since 2×21264981² = 904398833860722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1 + ... + 6521.

It is an arithmetic number, because the mean of its divisors is an integer number (3547968).

Almost surely, 2^21264981 is an apocalyptic number.

21264981 is the 6521-st triangular number and also the 3261-st hexagonal number.

It is an amenable number.

21264981 is a deficient number, since it is larger than the sum of its proper divisors (7118763).

21264981 is a wasteful number, since it uses less digits than its factorization.

21264981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7611.

The product of its digits is 6912, while the sum is 33.

The square root of 21264981 is about 4611.3968599547. The cubic root of 21264981 is about 277.0479874461.

The spelling of 21264981 in words is "twenty-one million, two hundred sixty-four thousand, nine hundred eighty-one".