21047155 has 8 divisors (see below), whose sum is σ = 26586000. Its totient is φ = 15951456.

The previous prime is 21047153. The next prime is 21047183. The reversal of 21047155 is 55174012.

21047155 = 117² + 118² + ... + 401².

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21047155 - 2¹ = 21047153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21047153) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 110680 + ... + 110869.

It is an arithmetic number, because the mean of its divisors is an integer number (3323250).

Almost surely, 2^21047155 is an apocalyptic number.

21047155 is a deficient number, since it is larger than the sum of its proper divisors (5538845).

21047155 is a wasteful number, since it uses less digits than its factorization.

21047155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221573.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21047155 is about 4587.7178422392. The cubic root of 21047155 is about 276.0987665496.

The spelling of 21047155 in words is "twenty-one million, forty-seven thousand, one hundred fifty-five".