21953555 has 24 divisors (see below), whose sum is σ = 29205456. Its totient is φ = 15744960.

The previous prime is 21953537. The next prime is 21953563. The reversal of 21953555 is 55535912.

It is not a de Polignac number, because 21953555 - 2⁸ = 21953299 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 309170 + ... + 309240.

It is an arithmetic number, because the mean of its divisors is an integer number (1216894).

Almost surely, 2^21953555 is an apocalyptic number.

21953555 is a deficient number, since it is larger than the sum of its proper divisors (7251901).

21953555 is an equidigital number, since it uses as much as digits as its factorization.

21953555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227 (or 156 counting only the distinct ones).

The product of its digits is 33750, while the sum is 35.

The square root of 21953555 is about 4685.4620903386. The cubic root of 21953555 is about 280.0066112385.

It can be divided in two parts, 2195 and 3555, that multiplied together give a triangular number (7803225 = T₃₉₅₀).

The spelling of 21953555 in words is "twenty-one million, nine hundred fifty-three thousand, five hundred fifty-five".