21621457 has 16 divisors (see below), whose sum is σ = 25949952. Its totient is φ = 17752320.

The previous prime is 21621437. The next prime is 21621463. The reversal of 21621457 is 75412612.

It is a cyclic number.

It is not a de Polignac number, because 21621457 - 2⁷ = 21621329 is a prime.

It is a super-3 number, since 3×21621457³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5113 + ... + 8329.

It is an arithmetic number, because the mean of its divisors is an integer number (1621872).

Almost surely, 2^21621457 is an apocalyptic number.

It is an amenable number.

21621457 is a deficient number, since it is larger than the sum of its proper divisors (4328495).

21621457 is a wasteful number, since it uses less digits than its factorization.

21621457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3288.

The product of its digits is 3360, while the sum is 28.

The square root of 21621457 is about 4649.8878481099. The cubic root of 21621457 is about 278.5875166940.

The spelling of 21621457 in words is "twenty-one million, six hundred twenty-one thousand, four hundred fifty-seven".