21291272 has 8 divisors (see below), whose sum is σ = 39921150. Its totient is φ = 10645632.

The previous prime is 21291269. The next prime is 21291287. The reversal of 21291272 is 27219212.

It can be written as a sum of positive squares in only one way, i.e., 12013156 + 9278116 = 3466^2 + 3046^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330697 + ... + 1330712.

Almost surely, 2^21291272 is an apocalyptic number.

It is an amenable number.

21291272 is a deficient number, since it is larger than the sum of its proper divisors (18629878).

21291272 is a wasteful number, since it uses less digits than its factorization.

21291272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2661415 (or 2661411 counting only the distinct ones).

The product of its digits is 1008, while the sum is 26.

The square root of 21291272 is about 4614.2466340671. The cubic root of 21291272 is about 277.1621166944.

The spelling of 21291272 in words is "twenty-one million, two hundred ninety-one thousand, two hundred seventy-two".