21156051 has 16 divisors (see below), whose sum is σ = 33350400. Its totient is φ = 11671968.

The previous prime is 21156049. The next prime is 21156053. The reversal of 21156051 is 15065112.

It is an interprime number because it is at equal distance from previous prime (21156049) and next prime (21156053).

It is not a de Polignac number, because 21156051 - 2¹ = 21156049 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21156053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16761 + ... + 17978.

It is an arithmetic number, because the mean of its divisors is an integer number (2084400).

Almost surely, 2^21156051 is an apocalyptic number.

21156051 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21156051 is a deficient number, since it is larger than the sum of its proper divisors (12194349).

21156051 is a wasteful number, since it uses less digits than its factorization.

21156051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34778.

The product of its (nonzero) digits is 300, while the sum is 21.

The square root of 21156051 is about 4599.5707408409. The cubic root of 21156051 is about 276.5741173645.

The spelling of 21156051 in words is "twenty-one million, one hundred fifty-six thousand, fifty-one".