21553953 has 4 divisors (see below), whose sum is σ = 28738608. Its totient is φ = 14369300.

The previous prime is 21553951. The next prime is 21553957. The reversal of 21553953 is 35935512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21553953 - 2¹ = 21553951 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21553951) 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, 3592323 + ... + 3592328.

It is an arithmetic number, because the mean of its divisors is an integer number (7184652).

Almost surely, 2^21553953 is an apocalyptic number.

It is an amenable number.

21553953 is a deficient number, since it is larger than the sum of its proper divisors (7184655).

21553953 is an equidigital number, since it uses as much as digits as its factorization.

21553953 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7184654.

The product of its digits is 20250, while the sum is 33.

The square root of 21553953 is about 4642.6235040115. The cubic root of 21553953 is about 278.2972899251.

The spelling of 21553953 in words is "twenty-one million, five hundred fifty-three thousand, nine hundred fifty-three".