21949851 has 16 divisors (see below), whose sum is σ = 36488448. Its totient is φ = 11402400.

The previous prime is 21949847. The next prime is 21949853. The reversal of 21949851 is 15894912.

It is not a de Polignac number, because 21949851 - 2² = 21949847 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21949853) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47280 + ... + 47741.

It is an arithmetic number, because the mean of its divisors is an integer number (2280528).

Almost surely, 2^21949851 is an apocalyptic number.

21949851 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21949851 is a deficient number, since it is larger than the sum of its proper divisors (14538597).

21949851 is a wasteful number, since it uses less digits than its factorization.

21949851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95042.

The product of its digits is 25920, while the sum is 39.

The square root of 21949851 is about 4685.0668084884. The cubic root of 21949851 is about 279.9908627971.

The spelling of 21949851 in words is "twenty-one million, nine hundred forty-nine thousand, eight hundred fifty-one".