21551145 has 64 divisors (see below), whose sum is σ = 44015616. Its totient is φ = 8743680.

The previous prime is 21551143. The next prime is 21551171. The reversal of 21551145 is 54115512.

It is not a de Polignac number, because 21551145 - 2¹ = 21551143 is a prime.

It is a super-2 number, since 2×21551145² = 928903701622050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21551143) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 54087 + ... + 54483.

It is an arithmetic number, because the mean of its divisors is an integer number (687744).

Almost surely, 2^21551145 is an apocalyptic number.

It is an amenable number.

21551145 is an abundant number, since it is smaller than the sum of its proper divisors (22464471).

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

21551145 is a wasteful number, since it uses less digits than its factorization.

21551145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 470.

The product of its digits is 1000, while the sum is 24.

The square root of 21551145 is about 4642.3210789432. The cubic root of 21551145 is about 278.2852040875.

Adding to 21551145 its reverse (54115512), we get a palindrome (75666657).

It can be divided in two parts, 215 and 51145, that added together give a triangular number (51360 = T₃₂₀).

The spelling of 21551145 in words is "twenty-one million, five hundred fifty-one thousand, one hundred forty-five".