21737961 has 12 divisors (see below), whose sum is σ = 35884992. Its totient is φ = 12421656.

The previous prime is 21737953. The next prime is 21737971. The reversal of 21737961 is 16973712.

It is a happy number.

It is not a de Polignac number, because 21737961 - 2³ = 21737953 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21737971) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 172461 + ... + 172586.

It is an arithmetic number, because the mean of its divisors is an integer number (2990416).

Almost surely, 2^21737961 is an apocalyptic number.

21737961 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21737961 is a deficient number, since it is larger than the sum of its proper divisors (14147031).

21737961 is a wasteful number, since it uses less digits than its factorization.

21737961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345060 (or 345057 counting only the distinct ones).

The product of its digits is 15876, while the sum is 36.

The square root of 21737961 is about 4662.3986316058. The cubic root of 21737961 is about 279.0869964184.

The spelling of 21737961 in words is "twenty-one million, seven hundred thirty-seven thousand, nine hundred sixty-one".